Aging Clin Exp Res DOI 10.1007/s40520-015-0368-6
ORIGINAL ARTICLE
Episodic future thinking: the role of working memory and inhibition on age-related differences Michela Zavagnin1 • Rossana De Beni1 • Erika Borella1 • Barbara Carretti1
Received: 30 January 2015 / Accepted: 24 April 2015 Ó Springer International Publishing Switzerland 2015
Abstract The ability to remember past events and imagine future events (episodic future thinking—EFT) has been shown to decline with aging. However, only few studies have analyzed the cognitive mechanisms involved in EFT in both young and older adults. The present study examined the role of working memory and inhibition on age-related differences between young and older adults in EFT, in response to short sentences reflecting common events, some of which were repeated in both conditions (past and future). Thirty-seven young and 36 older adults completed an adapted version of the autobiographical interview, in which sentences were presented. Results showed that processing resources explained a significant part of the variance in the amount of details; in particular, inhibition explained the amount of external details produced in the future condition. In addition, using sentences, the older group did not differ from the young adults in terms of the proportion of internal details recalled in the past condition, whereas they produced a lower proportion of internal details in the future condition. The effect of using structured material was reinforced by repeating some sentences in the past. Further, only older adults rated the remembered episodes as more emotionally salient and relevant than the imagined ones. Age-related differences between young and older adults in EFT appear to depend & Michela Zavagnin [email protected] & Erika Borella [email protected] & Barbara Carretti [email protected] 1
Department of General Psychology, University of Padova, Via Venezia 8, 35131 Padua, Italy
on the type of material used, on basic mechanisms of cognition, and are characterized by both quantitative and qualitative differences. Keywords Episodic future thinking Aging Working memory Inhibition
Introduction A large number of studies showed a decline of executive functions with age [1, 2] that affect, in particular, working memory [3–6]. Several hypotheses have been advanced to explain age-related changes in working memory (WM), one of these is the inhibitory hypothesis [7] that proposed that the tendency of older adult to keep irrelevant information active in WM, or to be disturbed by this information defines the decrease in WM capacity. According to Hasher and Zacks [7], aging involves a decrease in the effectiveness and efficiency of the ability to control interference, as confirmed by a wide variety of task and procedures [e.g., 8–12]. Inhibition, according to Hasher and Zacks’ view, is central as efficient inhibitory mechanisms permit to focus on the relevant task goals without been distracted by other irrelevant information. Poor inhibition not only limits, but also damages cognitive performance by allowing not relevant information to intrude and consume limited storage capacity, and permitting the use of resources for the processing of irrelevant information [13]. There are data suggesting that the decrease in inhibitory abilities is more evident after the age of 70 years [e.g., 14]; old–old adults, in fact, are less able to inhibit irrelevant information, and more likely to retrieve them [e.g., 15]. Several studies demonstrated that poor inhibitory mechanisms are associated with a variety of problems older
123
Aging Clin Exp Res
adults encounter in complex cognitive tasks. In this context, we refer to the possibility that age-related decline in WM and inhibition, together with decline in episodic memory [16], could be involved in older adults’ poor performance in tasks requiring to project events involving the self into the future, i.e., episodic future thinking—EFT, that is essential to program personal life. Episodic future thinking could be conceived, according to episodic simulation hypothesis proposed by Schacter and Addis [17], as the ability to flexibly recombine details drawn from past experiences, own personal goals or events to construct an event that could plausibly occur in the near future. In this sense, it has been suggested that both remembering past and imagining future events are tightly related as they require the retrieval of information from memory, but imagining future scenarios could be considered a more demanding task because it entails the additional cognitive effort needed to recombine past memories in a plausible future situation involving the self [18]. Several studies demonstrated that EFT is affected by aging, in fact older people produce more semantic details and fewer internal episodic ones than younger people, both when they describe past events and—even more—when imagining the future [19, 20]. Often, when older adults have to imagine a future event, they simply recast past events in a future time, due to an age-related difficulty in recombining episodic details from various episodes [21]. Older adults also produce more emotional details than younger people [22]. These age-related differences in the qualities of people’s descriptions of past and future events have been accounted for in models of autobiographical memory [e.g., 23], which distinguish between the episodic component of autobiographical memory (which is affected by aging) and the semantic component, containing a more abstract autobiographical knowledge (which is preserved in aging) [19]. Being less able to create episodic details, particularly in the case of the more demanding future condition, older adults probably rely on semantic components of autobiographical memory to fill the gaps [22]. In view of these results, executive processes and working memory could play a role in explaining age differences in EFT. For example, it has been demonstrated, in young adults, that executive processes may support the strategic aspects of retrieving autobiographical details [24] and recombining them into future scenarios [25]. Among the various executive processes, Suddendorf and Corballis [26] have suggested that remembering past events and imagining future ones require a processing space where information is temporarily maintained and manipulated (i.e. WM). D’Argembeau et al. [25] examined in young adults the contribution of some executive function (verbal and semantic fluency) and working memory (measured with the
123
letter-number sequencing task taken from WAIS III, [27]) tasks to different dimension of episodic future thinking performance, i.e., fluency (e.g., how many unique future events can a person generate in 1 min), specificity (e.g., whether a person can construct a unique potential future event), and details (e.g., how many specific episodic details can a person produce about a possible future event). D’Argembeau et al. [25] reported that the factor representing executive processes was the only independent predictor of autobiographical fluency, autobiographical specificity, and the amount of episodic details. More recently, Hill and Emery [28] deepened the role of working memory for EFT, adapting the distinction made by D’Argembeau et al. [25] and presenting four measures of WM. Hill and Emery [28] demonstrated that the WM composite score was significantly correlated with future episodic specificity, over and above the relationship between future and past specificity. In contrast WM was not associated with the other EFT measures. Few studies examined this issue in older adults. For example Addis et al. [22] reported that the performance in the Digit backward span correlated with internal details produced, and this relationship was significant for future events. Another indirect suggestion of the relevance of executive processes and WM for EFT come from the study by Gaesser et al. [29] who showed that older adults performance decrease not only in imagination future events but also in picture description, and memory tasks; that appears to indicate that mechanisms other than episodic memory are also relevant to understanding EFT [see also 30]. On the basis of this short review of the existing data, the main goal of our study was to shed light on the underlying mechanisms that might explain EFT and the decrease of this ability in older adults. Based on the previous studies, we focused on WM and inhibition, which may plausibly be responsible for the declining recollection of specific past events and building of episodic future events with age. Since past events serve a directive function for EFT in a dynamic interaction, WM may bridge temporal discontinuities, integrating information from long-term memory stores with perceptual information for the purpose of episode generation in the past and future. Inhibition may also influence EFT performance, since it is believed to account for cognitive aging, and has been shown to mediate agerelated differences in WM. The role of these processes was assessed in a EFT task where a modified version of Galton’s classic paradigm, i.e., sentences reflecting common events, was used instead of cue words. This choice was driven by published data suggesting that people, and older adults especially, can produce more details if they are given more structured elements than single cue words [e.g., 31]. This may be because they are
Aging Clin Exp Res
facilitated in developing an episode with a consequently lower demand in terms of cognitive effort and resources. Consistently with this view, Levine et al. [32] showed that older adults could produce more episodic details in recalling past events when they are specifically probed to retrieve further details; under this condition, the proportion of episodic details increased in older adults, reducing the age effect seen in standard retrieval conditions (with no specific probe). A similar facilitating effect was observed in amnesic patients through the presentation of structured cue (i.e., scenarios that were explicit self-relevant and potentially plausible event in the future) both in remembering past events and in imaging future ones [33, 34]. In the current study, therefore, participants were cued with sentences about prototypical events (which may refer to script) in people’s lives, such as marriages, holidays, births, etc. Judging from the literature, we assumed that using sentences would help participants to generate specific episodic events, and this could apply particularly to older adults, especially when they have to imagine the future. We assessed age differences in events production in terms of their specificity (episodic vs. semantic details) vividness, emotional salience and importance to the young and older adults’ personal life, comparing past and future scenarios. In line with previous studies, we expected older adults to rate past events as more salient and relevant than future events. These analyses on the type of detail and the valence of the events described by participants [as proposed by 19–21, 25] enabled us to conduct a detailed quantitative analysis without neglecting the influence of subjective variables that could change with aging. A complementary goal was to analyze the effect of repetition of some cue sentences in both the past and the future condition. According to the episodic simulation hypothesis, because future events depend on the flexible recombination of details drawn from memory of past experiences, using the same cue in both conditions could make it easier to describe events (especially in the future) because they have already been activated by a previous presentation under the non-repeated condition. An opposite pattern of results could emerge, however. The use of sentences representing common situations and the repetition, due to a previous memory activation, might also lead to: (i) a greater production of stereotypic information unrelated to personal events; and (ii) a repetition of the same already-reported events.
Method
older adults (12 males and 24 females, mean age 62.11, SD 2.33). The younger adults were students or workers, while the older adults were workers or retired, and members of voluntary associations. All participants were Italian native speakers and volunteered for the study. None of them met the exclusion criteria proposed by Crook et al. [35] (i.e., a history of head trauma; any neurological or psychiatric illness; history of brain fever; dementia or any other state of altered consciousness; use of benzodiazepines in the last 3 months; use of illicit drugs; visual, auditory and/or motor impairment; any symptomatic cardiovascular conditions, breathing problems or diseases with the potential for causing cognitive impairments), or a Mini-Mental State score [36] below 27. The two age groups did not differ (p [ 0.05) in Wechsler Adult Intelligence Scale—revised (WAIS–R) vocabulary scores [37], or personal satisfaction scores on the Well-Being Questionnaire [38]. Older participants performed above the cutoff for their age and education in terms of vocabulary [Italian norms by 39], well-being (measured with the well-being questionnaire by 40) and WM (the Listening Span Test; see Italian norms, 40). The characteristics of the sample are summarized in Table 1.
Materials Autobiographical interview The stimuli consisted of 25 sentences representing common events1 (e.g., a christmas lunch, a dinner with colleagues); 10 were presented in the past condition, 10 in the future, and 5 in both. For each participant, the content of the sentences was randomly placed in the past or future, except for the five sentences repeated in both conditions, which were the same for all participants. The order of presentation of the past and future conditions was counterbalanced for each participant, so the repeated events were presented in the future for half of the participants (first in the past, then in the future condition), and in the past for the other half (first in the future, then in the past condition), in a counterbalanced fashion. Participants were encouraged to retrieve or imagine temporally and contextually specific events. Future events had to be plausible and both past and future events were not to span more than 1 day. Participants were asked to indicate the period in their life when the event
Participants The sample consisted of thirty-seven younger adults (17 males and 20 females, mean age 24.89, SD 2.33) and 36
1
The events were considered to be very common by three independent judges.
123
Aging Clin Exp Res Table 1 Characteristics [mean (M) and standard deviation (SD)] of participants by age group
Younger adults
Older adults
M
SD
M
SD
Age
24.89
2.33
62.11
2.33
Vocabulary
59.97
5.69
58.83
6.74
Well-being
32.43
3.74
32.58
4.23
Listening Span Test, words recalled correctly
30.22
4.68
23.42
5.91
0.02
0.03
0.09
0.09
Proportion of intrusions errors in the Listening Span Test
occurred or was expected to occur.2 The maximum time allowed to describe each episode was 3 min. For each sentence cue, participants qualitatively rated their past or future episode as suggested by D’Argembeau and Van der Linden [41] using a 5-point scale as follows: (a) relevance attributed to the episode (from 1: insignificant, irrelevant to my life, to 5: extremely relevant, a turning point in my life); (b) vividness of the episode (from 1: no image, I can only think about the situation, to 5: perfectly clear and as vivid as normal vision); (c) emotional importance of the episode (from 1: emotionally neutral, it arouses no emotion in me, to 5: extremely important, I have strong feelings about it). Scoring The qualities of participants’ recollections and simulations were estimated using an adapted version of the standardized scoring procedure developed by Levine et al. [32]. To be more precise, internal details (pertinent to the proposed sentence, and specific to the time and place) and external details (unassociated with the proposed sentence, semantic knowledge, repeated or unrealistic information) were identified for each past and future event that participants described. Listening Span Test (LST) [14] This task, originally devised by Daneman and Carpenter [42], consisted of sequences containing an increasing 2
Although all participants were asked to indicate the period in their life when the event occurred or was expected to occur, data recording was available for a limited number of participants (30 young adults; 13 older adults). The tendency emerging from available data was explored with a 2 (young vs. old) by 2 (past vs. future) ANOVA on the number of years reported for past events and future events. Results showed a significant Age x Condition interaction, F(1,41) = 7.44, p \ 0.01 g2p = 0.15: older adults (M 14.71, SD 8.42) rated their past events as having occurred a longer time before than young adults (M 6.38, SD 3.21). Moreover, only older adults reported events in the past as being more remote from the present than was the case for events imagined in the future (p = 0.004). No age-related differences were found for the future condition (young adults: M 6.84, SD 7.23; older adults: M 6.26, SD 8.28). Age-related differences in the time elapsing between the event and the present were only seen for past events.
123
number (from 2 to 6) of simple sentences. The sequences of sentences were grouped into four sets of four sequences. Twenty sentences were presented in each set (giving a total of 80 sentences), with an interval of 1.5 s between one sentence and the next. Participants were asked to listen to each sentence, judge its plausibility (i.e., say whether it was true or false) and retain the last word. At the end of each set of sentences, participants had to recall the last words of all the sentences in their order of presentation. The task was preceded by two practice trials. The total number of final words correctly recalled during the test was considered the measure of the individuals’ WM capacity. Intrusion errors (i.e., words recalled that were contained in the sentences but were not final words) were also computed. The purpose of this procedure was to measure the individuals’ ability to exhibit control over the permanence of information in their WM [e.g., 14, 43], i.e., inhibitory control. Procedure The experiment was conducted in two sessions taking 2.5 h altogether. The health history interview was conducted in the first session, when the core part of the study was also introduced, explaining the notion of mental imagery, with examples of imagining future and recalling past events. Then the sentences were presented and the participants’ descriptions of events were recorded. The Well-Being questionnaire [38] was administered in between the presentation of the sentences in the two temporal conditions (past and future) to avoid any facilitation effects of the former condition on the latter. The second session was dedicated to the Listening Span Test [40] and the Vocabulary subtest [WAIS-R, 37]. Transcripts of participants’ descriptions were subsequently segmented into various categories by two trained raters, who were unaware of the study hypotheses. Using Cohen’s kappa (K), inter-rater agreement for scoring of internal and external details was high ([0.90).
Aging Clin Exp Res
Results Processing resources: WM and inhibition To assess age-related differences in WM capacity and inhibition, two separate one-way ANOVA were run on: (i) the number of words correctly recalled in the Listening Span Test; and (ii) the proportion of intrusion errors in the Listening Span Test, i.e., the number of intrusions errors/ number of correct items recalled (see Table 1 for descriptive statistics). Working memory task Our results for the number of words recalled correctly in the Listening Span Test showed a main effect of group, F(1,71) = 35.89, p \ 0.001, g2p = 0.34; the young adults recalled more words than the older adults (MDiff. = 7.30, p \ 0.001) (see Table 1). Intrusion errors-inhibitory measure There was a significant main effect of Group on the proportion of intrusion errors in the Listening Span Test, F(1,71) = 19.31, p \ 0.001, g2p = 0.21: the older adults produced a higher proportion of intrusion errors than their younger counterparts (MDiff. = 0.08, p \ 0.001) (see Table 1).
and condition (past vs. future) for the repeated measures, on: (i) the relevance of the events described; (ii) the vividness of the events described in response to the sentences; (iii) the emotional importance of the events described in the past and in the future. For all the analyses, the interactions were broken down using post hoc pairwise comparisons with Bonferroni’s correction at p \ 0.05, adjusted for multiple comparisons. Mean number of internal and external details For the internal details (see Table 2), the results showed that the main effect of Group was significant, F(1,71) = 17.67 p \ 0.001 g2p = 0.20, indicating that young adults produced more details than older adults (MDiff. = 6.29, p \ 0.001). The main effect of Condition was also significant, F(1,71) = 43.06 p \ 0.001 g2p = 0.38: more details were given for past than for future events (MDiff. = 6.25, p \ 0.001). The Group 9 Condition interaction was not significant, however, F \ 1. For external details, the results showed the main significant effect of Group, F(1,71) = 5.00 p \ 0.05 g2p = 0.07, indicating that young adults produced less external details than older adults (MDiff. = -0.98, p \ 0.001. No other significant effects emerged: condition F \ 1; group 9 condition F \ 1 (see Table 2). The effect of repetition on internal and external details
Autobiographical interview First, the mean number of details produced by participants was analyzed using two separate repeated measures ANOVA on internal and external details, with Group (young, older adults) as a between-subjects factor and Condition (past or future) as a within-subject factor. This was done because the range for the details differed considerably between the two categories (the range for internal details was from 10 to 50, while for external details it was from 0 to 10). Second, the effect of repetition on the production of events in the past and future was analyzed, again distinguishing between internal and external details. Two separate ANOVA were run on internal and external details, one for the past condition and the other for the future one, with Group (young, older adults) as a between-subjects factor and repetition (repeated vs. non-repeated) as a within-subject factor. A separate analysis was necessary because half of the participants were presented with repeated sentences in the past, the other half with repeated sentences in the future, using a counterbalanced method. A series of repeated-measures ANOVA were run, with group (young vs. older adults) as a between-subjects factor,
Analyzing the mean number of internal details for repeated sentences in the past condition, our results showed that the main effect of Group, F \ 1, and the Group 9 Repetition interaction, F(1,35) = 2.50 p = 0.12 g2p = 0.07, were not significant. On the other hand, the main effect of Repetition was significant, F(1,35) = 6.53 p \ 0.05 g2p = 0.16, more internal details being given for repeated than for non-repeated sentences (MDiff. = 2.33, p \ 0.05) (see Table 2).
Table 2 Mean number of internal and external details in sentences presented only once or repeated, by condition (past vs. future) and age group Younger adults
Older adults
M
SD
M
SD
27.46 1.39
9.82 1.50
21.96 2.10
6.66 2.85
Internal
22.00
8.74
14.91
3.33
External
0.98
1.50
2.22
2.62
Past Internal External Future
123
Aging Clin Exp Res
When the repeated sentences were presented in the future condition, we found a main effect of Group, F(1,34) = 6.25 p \ 0.05 g2p = 0.16, indicating that the younger adults included more internal details than older adults (MDiff. = 7.16, p \ 0.05). The main effect of Repetition, F(1,34) = 2.19 p = 0.15 g2p = 0.06, and the Group 9 Repetition interaction, F(1,34) = 2.66 p = 0.11 g2p = 0.07, were not significant. The results for external details revealed no significant differences (F \ 1) when repeated sentences were presented in the past condition. Instead, when the effect of repetition in the future was analyzed, the results showed a significant Group x Repetition interaction, F(1,34) = 7.81 p \ 0.01 g2p = 0.19, indicating that younger adults included more external details for repeated than for nonrepeated sentences (p = 0.011). No other effects were found (F \ 1) (see Table 2). Relevance of the events produced The main effects of Group and Condition were not significant (F \ 1), but the Group x Condition interaction was significant, F(1,71) = 10.71 p \ 0.01 g2p = 0.14, and indicated that the young adults considered imagined events (future condition) more significant (MDiff. = 0.22, p = 0.008) than those remembered from their past (see Table 3). Vividness of the events described The main effect of Group, F(1,71) = 2.46 p [ 0.05 g2p = 0.03, and the Group x Condition interaction, F(1,71) = 1.86 p = 0.18 g2p = 0.03, were not significant, but the main effect of Condition was significant, F(1,71) = 31.29 p \ 0.001 g2p = 0.31, indicating that events from the past generated more vivid mental images than those set in the future (MDiff. = 0.33, p \ 0.001) (see Table 3). Table 3 Mean value (1–5 Likert scale) of vividness, and emotional salience attributed to past and future events by age group Younger adults M
Older adults SD
M
SD
Relevance Past
2.89
0.43
3.13
0.44
Future
3.11
0.53
2.96
0.54
Vividness Past
3.83
0.52
3.74
0.45
Future
3.59
0.67
3.33
0.49
Salience Past
3.00
0.53
3.34
0.41
Future
3.25
0.54
3.11
0.52
123
Emotional importance of the events described The main effects of Group and Condition were not significant (F \ 1 for both). The Group x Condition interaction was significant, F(1,71) = 16.82 p \ 0.001 g2p = 0.19: in the past condition, events were rated as more salient by the older than by the younger adults (p = 0.004), whereas in the future condition, there were no significant differences between the two groups. The younger adults rated imagined events as more emotionally salient than remembered ones (p = 0.003), while the older adults rated remembered events as having a greater emotional charge than imagined ones (p = 0.008) (see Table 3). Correlations Correlation analyses (see Table 4) were conducted to enable a preliminary assessment of the relationship between age, type of detail (internal, external) in response to sentences used in the past or future conditions, and participants’ performance in the Listening Span Test, i.e., words correctly remembered (which is a measure of WM capacity) and proportion of intrusion errors (which is an indicator of inhibitory control-inhibitory mechanisms). As expected, our findings showed a negative correlation between age and internal details, which was large [according to 44] for the future condition (r = -0.59), but small for the past (r = -0.30). Age also correlated negatively with processing resources (WM r = -0.59), and inhibitory mechanisms (r = 0.49), consistently with the literature [45]. A small correlation was found between age and external details, however, but only in the past (r = 0.28). The mean number of internal details reported for past events correlated moderately with the number of internal details reported in the future condition (r = 0.51), and of external ones in the past with those in the future (r = 0.46) in line with the episodic simulation hypothesis. In both conditions, the mean number of internal details also correlated with WM performance (r = 0.30 and r = 0.33, for the past and future, respectively), while a small negative correlation emerged between the proportion of internal details in the future and the errors in the WM task (r = -0.32), suggesting that participants who produced more internal details in the future had more efficient inhibitory mechanisms too. Since the aim of our analysis was exploratory; however, these correlations should be interpreted with caution because no corrections were applied. Regression analyses Hierarchical regression analyses were run to estimate the percentage of variance for the internal and external details
Aging Clin Exp Res Table 4 Correlations between age, details (internal, external) generated in response to sentences presented only in past or future conditions, working memory (Listening Span Test), and inhibition (intrusion errors in the Listening Span Test) 1
2
3
4
5
6
Age Past internal details
-0.30*
Future internal details
-0.50**
0.51**
Past external details
0.28*
0.27*
0.02
Future external details
0.17
0.22
0.10
-0.59**
0.30*
0.33**
-0.09
-0.01
-0.32**
0.37
0.06
Listening Span Test, words recalled correctly Proportion of intrusions errors in the Listening Span Test
0.49**
-0.11
0.46** -0.47**
N = 73 LST listening span test * p \ 0.05; ** p \ 0.01
produced (criterion variables), which was explained by age and processing resources (WM, inhibition), and the same type of detail (internal or external) being produced in the other temporal condition (i.e., the dependent variable was internal details in the future when the past condition was analyzed, and internal details in the past when the future condition was considered). Two different models were used, which differed in the order of the variables entered, to assess the role of age vs. cognitive resources and details in either temporal condition; the latter predictors were regressed before and after the age variable. In Model 1, age was entered in step 1. WM, inhibition and internal details in the future (when the criterion variable was internal details in the past), or in the past (when the criterion variable was internal details in the future) were entered in Step 2. In Model 2, the order of entry of the variables was: WM and inhibition and internal details (step 1), and age (step 2). Cook’s distance was computed to detect outliers (cook’s distance [1) on the criterion and predictor variables, but none were found. Nor did the variance inflation factors or tolerance criteria indicate any significant multicollinearity [45]. For the internal details given in the past condition, Model 1 showed that age explained a significant part of the variance (R2 = 0.09, p \ 0.01), while processing resources and internal details in the future condition (step 2) contributed to explaining an additional 6.7 % of the variance; the internal details in the future conditions (b = 0.49, p \ 0.001) was the unique salient predictors. When age was entered in the last step, however (Model 2), only processing resources and internal details explained a significant part of the variance (R2 = 0.30, p \ 0.001), while age was no longer a significant predictor. In fact, the mean number of internal details in the future conditions (b = 0.49, p \ 0.001) made a unique contribution to the variance explained.
As for the internal details produced in the future condition, Model 1 showed that age explained a significant part of the variance in step 1 (R2 = 0.25, p \ 0.001), while processing resources and internal details in the past condition (step 2) contributed to explaining an additional 6.1 % of the variance; age (b = -0.35, p \ 0.01) and the mean number of internal details in the future conditions (b = 0.42, p \ 0.001) were the unique salient predictors. Model 2 showed the same results, in fact processing resources and internal details in the past (Step 1) explained a significant part of the variance (R2 = 0.34, p \ 0.001), and age (Step 2) explaining an additional 8 % of variance: Age (b = -0.35, p \ 0.01) and the mean number of internal details in the future conditions (b = 0.42, p \ 0.001) were the unique salient predictors. When we looked at the external details produced in the past condition, Models 1 and 2 both showed that only processing resources and external details in the future condition explained a significant part of variance (Model 1, R2 = 0.24, p \ 0.01; Model 2, R2 = 0.23, p \ 0.01). The mean number of external details in the future conditions (b = 0.49, p \ 0.001) was the unique salient predictors. Finally, when it came to external details produced in the future condition, Model 1 showed that age explained a significant part of variance (R2 = 0.08, p \ 0.05), processing resources and external details in the past (Step 2) explained an additional 9.2 % of variance. Intrusion errors in Listening Span Test (b = 0.35, p \ 0.01) and the mean number of external details in the past conditions (b = 0.42, p \ 0.001) were the unique salient predictors. Model 2 showed that only processing resources and external details in the past (step 1) explained a significant part of variance (R2 = 0.33, p \ 0.05); intrusion errors (b = 0.38, p \ 0.01) and the mean number of external details in the past (b = 0.44, p \ 0.001) were the unique salient predictors. Overall, these results show that, while for internal details only age and internal details in the other condition
123
Aging Clin Exp Res
explaining the variance, for the external details the role of the predictors changed, depending on whether the past or future condition was considered. In the past condition, only the number of external details in the future condition contributed to the variance explained for internal details; in the future condition age and processing resource, in particular inhibition, accounted for the variance in the production of internal details imagined in the future. Comparison between the use of contextual information vs. specific cues in EFT In Table 5, we qualitatively compare the results, in terms of age-related differences, between the present study, in which contextual information (as provided by sentences) is used, and other studies adopting other procedures (words, or pictures as cues). The use of contextual information appears to advantage older adults with respect to the percentage of internal details.
Discussion The main goal of our study was to shed light on the EFT phenomenon, understanding the role of age and some processing resources (WM and inhibition) that are particularly sensitive to aging [45], since no previous studies addressed the influence of processing resources on EFT. Our results showed that internal details produced in the other experimental (future or past) condition and age influence internal details produced in the past and in the future condition. Further, and more interestingly, we found that only for the production of external details, the role of age and processing resources change depending on whether the past or future condition was involved. In fact, processing resources and the external details produced in the other experimental condition (that is in the future condition), predicted the mean number of external details produced in the past condition, on the one hand. On the other hand, age and inhibition explained external details produced in the future condition. Such a result suggests that, with aging, there is an increase in the external details produced and this appears to be related to the decrease in Table 5 Summary of the percentage of internal details produced, in remembered or imagined events, in different cueing conditions by age group (published in peer-reviewed journals)
123
References
the efficiency of inhibitory mechanisms. Further, because of the decline in inhibitory mechanisms, older people may have more difficulty in pursuing the goal of describing specific episodes, and this could cause the increase of irrelevant and semantic details. Moreover, these findings suggest that the nature of the close relationship between remembering the past and imagining the future is multidimensional. They also confirm that cognitive abilities that decline with age, such as WM and inhibition [7], may contribute to EFT performance [25]. Future studies should strive to adopt a multivariate design that includes other cognitive measures in order to shed light on EFT in aging. Regarding the assessment of age-related differences in the specificity and the subjective quality (relevance to the individuals’ personal life, vividness of the mental image, and emotional salience) of events produced in past and future conditions a modified version of the classic Galton paradigm was used (i.e., we used sentence cues instead of words). We felt that using sentence cues representing common life events might facilitate participants’ access to their personal autobiographical information and thus help them to bind episodic knowledge with possible future scenarios, especially for older adults [e.g. 32–34]. Some of the sentences were also presented in both past and future conditions; this permitted us to assess the presence of a facilitator effect to pre-activate episodic information that could be recombined to construct new episodes or to recall past episodes, particularly for older adults. The events produced in the past and future were broken down into internal and external details, and were rated qualitatively by the participants, as suggested by D’Argembeau and Van der Linden [41]. When we considered the mean number of internal details, all participants produced more details in the past than in the future condition, and younger adults produced more details than older adults. No age-related differences emerged in the mean number of external details produced. These results extend available data on the age-related reduction in episodic specificity for past events [32, 46] and show that contextual information (as provided by sentences) enables older adults to produce more on-task information than when the classic procedure is used, or more
Type of cue
Past Young (%)
Future Old (%)
Youn (%)
Old (%)
Current study
Sentences
94
92
94
87
Gaesser et al. [29]
Pictures
*84
*67
*87
*66
Addis et al. [21]
Personalized memory cue
*76
*60
*69
*55
Gamboz et al. [53]
Words
_
*69
_
*67
Addis et al. [22]
Words
*84
*56
*68
*51
Aging Clin Exp Res
specific cues [21, 29], as in previous studies (see Table 5). The benefit of contextual cues is also suggested by the fact that the mean number of semantic details produced did not differ between the two age groups, neither in the past nor in the future condition. A qualitative comparison with previous studies (see Table 5) showed that the percentage of internal details produced by our group of older adults was higher than in other, more facilitating cueing conditions— involving the use of pictures and personalized memory cues, for instance [21, 29]. Nevertheless, our results showed that age-related differences were still significant, particularly when the future condition was considered. Our use of repetition, involving some sentences being presented in both past and future conditions, also always had a beneficial effect when internal details were considered: repeating the same sentences in the past nullified any age-related differences, with all participants producing more internal details in the repeated than in the non-repeated sentences. Older adults were thus able to produce as many details as young adults (see Table 2). In line with our hypotheses, this pattern of findings suggests that using the same cue in both conditions favors the retrieval of internal details of events that have already been activated with the previous presentation (under the non-repeated condition), or may provide older adults with a sort of environmental support [47]. On the other hand, the use of repeated sentences in the future conditions did not influence the agerelated differences in the production of internal details, since younger adults continued to outperform elders. The use of sentences and their repetition, when participants are asked to remember past events at least, therefore, facilitate the production of autobiographical details, suggesting that the ability to do so depends on the type of cue used, and on its activation. As for external details, age-related differences were no more significant in the past and future condition. Repeating the sentences yielded the production of a higher rate of external details in the younger group, however, probably due to some interference effects. With respect to the quality of the descriptions of events, the older adults attributed more relevance and emotional salience to episodes in the past, probably because they tended to reinterpret their past in a more positive light [48]. This may also explain the non-significant difference between the two age groups when internal details for past events were examined, confirming that age-related differences are reduced or nullified when the information has some personal relevance or emotional valence for older adults [see 49]. In fact, there are a number of studies showing that older adults perform as well as younger when valenced material (i.e., affective stimuli such as positive pictures are used—the so-called positivity bias with aging) is presented [50]: the greater motivated tendency to focus
on positive stimuli may help reducing their cognitive difficulties typically shown with neutral material [51]. It would, therefore, be of interest to examine EFT using emotional stimuli as cues as well. In contrast, younger people see their future as more important and are more optimistic about it [52, 53]. This might partly explain the younger adults’ better performance in imagining future events. Younger people tend to structure their future around personal goals [54] and this seems to prompt a greater use of episodic details to describe future events [55]. On the other hand, participants in both age groups rated their mental images of possible future events as being less vivid than their memories—as expected—probably because future events are characterized by fewer contextual and sensory details than past events [56]. This impression is also supported by the fact that age-related differences were not significant when participants were asked to indicate when the event could occur in the future. This is just one possible interpretation, however, given the data recording problems relating to this aspect (see note 2). Despite our insightful results, the present study has some limitations that need to be mentioned, such as the fact that we did not include the classical use of word cues to elicit events and thereby draw a direct comparison with the benefits of using sentence cues emerging from our results. Our qualitative comparison conducted with previous studies nonetheless suggests that using sentence cues is a promising approach to the study of EFT. Future studies could thus try to use different types of cue to replicate and clarify the present findings. Further, it would be of interest to assess whether presenting sentences instead of words as cues helps people to imagine future scenarios as well as to recall past events (as the greater detail produced by participants in this study in response to sentences instead of word cues seems to suggest), or whether sentence cues favor the production of prototypical events instead. Our study design also meant that we could not establish whether or not the effect of repeating cues remained the same if they were repeated after being presented first in the past or in the future condition. In addition, no old–old group was considered in this study, which might have shed some light on how very old age influences the pattern of results described here. To sum up, our study shows that older adults produce less episodic information than younger people, whether they are remembering the past or imagining future events, and they tend to compensate by producing more semantic information. The present results highlight also the importance of considering also qualitative differences between young and older adults: age-related differences in narrative style and in the relevance personally attributed to events appear to explain older adults’ different performance in
123
Aging Clin Exp Res
remembering past and imagining future events. Further, the different involvement of processing resources in EFT casts light on the differences between the production of internal and external episodes in aging. Finally, the role of type of material used to elicit EFT, should be taken into account as a potential crucial variable, as using sentence cues, and repeating them, appears to facilitate older adults’ production of internal details, nullifying the above-mentioned age-related differences when they have to remember a past event. Acknowledgments The authors wish to thank Irene Grasso for helping in data processing. This work was supported by a grant from the Italian Ministry of Research and Education (Progetto PRIN: 2010P8LRP7_003). Conflict of interest
None.
Human and Animal Rights The study was conducted according to standards derived from the Declaration of Helsinki. Informed consent A written informed consent was obtained from every patient.
References 1. Kray J, Lindenberger U (2000) Adult age differences in task switching. Psychol Aging 15(1):126–147 2. Craik FIM, Bialystok E (eds) (2006) Lifespan cognition: Mechanisms of change. Oxford University Press, Oxford, pp 297–314 3. Salthouse TA (1990) Working memory as a processing resource in cognitive aging. Dev Rev 10(1):101–124 4. Daigneault S, Braun CM (1993) Working memory and the selfordered pointing task: further evidence of early prefrontal decline in normal aging. J Clin Exp Neuropsyc 15(6):881 5. Park DC, Lautenschlager G, Hedden T et al (2002) Models of visuospatial and verbal memory across the adult life span. Psychol Aging 17:299–320 6. Bopp KL, Verhaeghen P (2005) Aging and verbal memory span: a meta-analysis. J Gerontol B Psychol Sci Soc Sci 60:223–233 7. Hasher L, Zacks RT (1988) Working memory, comprehension, and aging: a review and a new view. Psychol Learn Motiv 22:193–225 8. Verhaeghen P, De Meersman L (1998) Aging and the stroop effect: a meta-analysis. Psychol Aging 13(1):120–126 9. Langenecker SA, Nielson KA, Rao SM (2004) fMRI of healthy older adults during stroop interference. Neuroimage 21(1):192–200 10. Hasher L, Lustig C, Zacks RT (2007) Inhibitory mechanisms and the control of attention. In: Conway A, Jarrold C, Kane M, Miyake A, Towse J (eds) Variation in working memory. Oxford University Press, New York, pp 227–249 11. Belanger S, Belleville S (2009) Semantic inhibition impairment in mild cognitive impairment: a distinctive feature of upcoming cognitive decline? Neuropsychology 23(5):592 12. Borella E, Delaloye C, Lecerf T et al (2009) Do age differences between young and older adults in inhibitory tasks depend on the degree of activation of information? Eur J Cogn Psychol 21(2):445–472
123
13. Harnishfeger KK, Bjorklund DF (1993) The ontogeny of inhibition mechanisms: A renewed approach to cognitive development. In: Howe ML, Pasnek R (eds) Emerging themes in cognitive development, vol 1. Springer-Verlag, New York 14. Borella E, Carretti B, De Beni R (2008) Working memory and inhibition across the adult life-span. Acta Psychol 128:33–44 15. Hamm VP, Hasher L (1992) Age and the availability of inferences. Psychol Aging 7:56–64 16. Craik FIM, Salthouse TA (eds) (2000) Handbook of aging and cognition, 2nd edn. Lawrence Erlbaum Associates, Hillsdale 17. Schacter DL, Addis DR (2007) The cognitive neuroscience of constructive memory: remembering the past and imagining the future. Philos T R Soc B 362:773–786 18. Addis DR, Pan L, Vu MA, Laiser N, Schacter DL (2009) Constructive episodic simulation of the future and the past: distinct subsystems of a core brain network mediate imagining and remembering. Neuropsychologia 47:222–238 19. Gamboz N, Brandimonte MA, De Vito S (2010) The role of past in the simulation of autobiographical future episodes. Exp Psychol 57:419–428 20. Gamboz N, De Vito S, Brandimonte MA et al (2010) Episodic future thinking in amnesic mild cognitive impairment. Neuropsychologia 48:2091–2107 21. Addis DR, Musicaro R, Pan L, Schacter DL (2010) Episodic simulation of past and future events in older adults: evidence from an experimental recombination task. Psychol Aging 25:369–376 22. Addis DR, Wong AT, Schacter DL (2008) Age-related changes in the episodic simulation of future events. Psychol Sci 19:33–41 23. Conway MA (2001) Sensory-perceptual episodic memory and its context: autobiographical memory. Philos T R Soc B 356:1375–1384 24. Rubin DC (2006) The basic-systems model of episodic memory. Perspect Psychol Sci 1:277–311 25. D’Argembeau A, Ortoleva C, Jumentier S et al (2010) Component processes underlying future thinking. Mem Cogn 38:809–819 26. Suddendorf T, Corballis MC (2007) The evolution of foresight: what is mental time travel, and is it unique to humans? Behav Brain Sci 30(3):299 27. Wechsler D (2000) Echelle d’intelligence pour adulte, 3rd edn. Editions du, Paris 28. Hill P, Emery LJ (2013) Episodic future thought: contributions from working memory. Conscious Cogn 22(3):677 29. Gaesser B, Sacchetti DC, Addis DR, Schacter DL (2011) Characterizing age-related changes in remembering the past and imagining the future. Psychol Aging 26:80–84 30. Squire L et al (2010) Role of the hippocampus in remembering the past and imagining the future. Proc Natl Acad Sci USA 107(44):19044 31. Zacks RT, Hasher L, Li KZH (2000) Human memory. In: Salthouse TA, Craik FIM (eds) Handbook of aging and cognition. Lawrence Erlbaum Associates, Mahwah 32. Levine B, Svoboda E, Hay JF et al (2002) Aging and autobiographical memory: dissociating episodic from semantic retrieval. Psychol Aging 17:677–689 33. Hurley N, Maguire EA, Vargha-Khadem F (2011) Patient HC with developmental amnesia can construct future scenarios. Neuropsychologia 49(13):3620 34. Race E, Keane MM, Verfaellie M (2011) Medial temporal lobe damage causes deficits in episodic memory and episodic future thinking not attributable to deficits in narrative construction. J Neurosci 31(28):10262–10269 35. Crook T, Bartus RT, Ferris SH et al (1986) Age associated memory impairment: proposed diagnostic criteria and measures
Aging Clin Exp Res
36.
37. 38.
39.
40.
41.
42. 43.
44. 45.
of clinical change-report of a national institute of mental health work group. Dev Neuropsychol 2:261–276 Folstein MF, Folstein SE, McHugh PR (1975) ‘‘Mini-mental state’’: a practical method for grading the cognitive state of patients for the clinician. J Psychiat Res 12:189–198 Wechsler D (1981) Wechsler adult intelligence scale-revised manual. The Psychological Corporation, New York De Beni R, Marigo C, Nava LA et al (2008) BEN-SSC. Benessere e invecchiamento, in De Beni, Borella, Carretti, Marigo e Nava, pp. 97–114 Orsini A, Laicardi C (2003) Wais-R e terza eta`. La natura dell’intelligenza nell’anziano: continuita` e discontinuita`. [WAISR and the third age. The nature of intelligence in elderly people: continuity and discontinuity]. Firenze, Giunti OS De Beni R, Borella E, Carretti B, et al (2008) BAC. Portfolio per la valutazione del benessere e delle abilita` cognitive nell’eta` adulta e avanzata [The assessment of well-being and cognitive abilities in adulthood and aging]. Firenze, Giunti OS D’Argembeau A, Van der Linden M (2004) Phenomenal characteristics associated with projecting oneself back into the past and forward into the future: influence of valence and temporal distance. Conscious Cogn 13:844–858 Daneman M, Carpenter PA (1980) Individual differences in working memory and reading. J Verb Learn Verb Be 19:450–466 De Beni R, Palladino P, Pazzaglia F et al (1998) Increases in intrusion errors and working memory deficit of poor comprehenders. Q J Exp Psychol A 51:305–320 Cohen J (1988) Statistical power analysis for the behavioral sciences. Lawrence Erlbaum, Hillsdale Borella E, Ghisletta P, de Ribaupierre A (2011) Age differences in text processing: the role of working memory, inhibition and processing speed. J Gerontol B Psychol Sci Soc Sci 66:311–320
46. De Beni R, Palladino P (2004) Decline in working memory updating through ageing: intrusion error analyses. Memory 12:7589 47. Craik FIM, Byrd M (1982) Aging and cognitive deficits: the role of attentional resources. In: Craik FIM, Trehub S (eds) Aging and cognitive processes. Plenum, New York, pp 191–211 48. Carstensen LL (2006) The influence of a sense of time on human development. Science 312:1913–1915 49. Mammarella N, Borella E, Carretti B et al (2013) Assessing affective working memory: evidence from age-related differences. Neuropsychol Rehabil 23(3):1–13 50. Mikels JA, Larkin GR, Reuter-Lorenz PA et al (2005) Divergent trajectories in the aging mind: changes in working memory for affective vs. visual information with age. Psychol Aging 20:542–553 51. Dolcos F, LaBar KS, Cabeza R (2004) Dissociable effects of arousal and valence on prefrontal activity indexing emotional evaluation and subsequent memory: an event-related fMRI study. Neuroimage 23:64–74 52. D’Argembeau A, Van der Linden M (2006) Individual differences in the phenomenology of mental time travel: the effect of vivid visual imagery and emotion regulation strategies. Conscious Cogn 15:342–350 53. Gamboz N, De Vito S, Brandimonte MA et al (2010) Episodic future thinking in amnesic mild cognitive impairment. Neuropsychologia 48(7):2091–2097 54. Austin JT, Vancouver JB (1996) Goal constructs in psychology: structure, process, and content. Psychol Bull 120:338–375 55. D’Argembeau A, Mathy A (2011) Tracking the construction of episodic future thoughts. J Exp Psychol 140:258–271 56. Szpunar KK (2010) Episodic future thought: an emerging concept. Perspect Psychol Sci 5:142–162
123
ORIGINAL ARTICLE
Episodic future thinking: the role of working memory and inhibition on age-related differences Michela Zavagnin1 • Rossana De Beni1 • Erika Borella1 • Barbara Carretti1
Received: 30 January 2015 / Accepted: 24 April 2015 Ó Springer International Publishing Switzerland 2015
Abstract The ability to remember past events and imagine future events (episodic future thinking—EFT) has been shown to decline with aging. However, only few studies have analyzed the cognitive mechanisms involved in EFT in both young and older adults. The present study examined the role of working memory and inhibition on age-related differences between young and older adults in EFT, in response to short sentences reflecting common events, some of which were repeated in both conditions (past and future). Thirty-seven young and 36 older adults completed an adapted version of the autobiographical interview, in which sentences were presented. Results showed that processing resources explained a significant part of the variance in the amount of details; in particular, inhibition explained the amount of external details produced in the future condition. In addition, using sentences, the older group did not differ from the young adults in terms of the proportion of internal details recalled in the past condition, whereas they produced a lower proportion of internal details in the future condition. The effect of using structured material was reinforced by repeating some sentences in the past. Further, only older adults rated the remembered episodes as more emotionally salient and relevant than the imagined ones. Age-related differences between young and older adults in EFT appear to depend & Michela Zavagnin [email protected] & Erika Borella [email protected] & Barbara Carretti [email protected] 1
Department of General Psychology, University of Padova, Via Venezia 8, 35131 Padua, Italy
on the type of material used, on basic mechanisms of cognition, and are characterized by both quantitative and qualitative differences. Keywords Episodic future thinking Aging Working memory Inhibition
Introduction A large number of studies showed a decline of executive functions with age [1, 2] that affect, in particular, working memory [3–6]. Several hypotheses have been advanced to explain age-related changes in working memory (WM), one of these is the inhibitory hypothesis [7] that proposed that the tendency of older adult to keep irrelevant information active in WM, or to be disturbed by this information defines the decrease in WM capacity. According to Hasher and Zacks [7], aging involves a decrease in the effectiveness and efficiency of the ability to control interference, as confirmed by a wide variety of task and procedures [e.g., 8–12]. Inhibition, according to Hasher and Zacks’ view, is central as efficient inhibitory mechanisms permit to focus on the relevant task goals without been distracted by other irrelevant information. Poor inhibition not only limits, but also damages cognitive performance by allowing not relevant information to intrude and consume limited storage capacity, and permitting the use of resources for the processing of irrelevant information [13]. There are data suggesting that the decrease in inhibitory abilities is more evident after the age of 70 years [e.g., 14]; old–old adults, in fact, are less able to inhibit irrelevant information, and more likely to retrieve them [e.g., 15]. Several studies demonstrated that poor inhibitory mechanisms are associated with a variety of problems older
123
Aging Clin Exp Res
adults encounter in complex cognitive tasks. In this context, we refer to the possibility that age-related decline in WM and inhibition, together with decline in episodic memory [16], could be involved in older adults’ poor performance in tasks requiring to project events involving the self into the future, i.e., episodic future thinking—EFT, that is essential to program personal life. Episodic future thinking could be conceived, according to episodic simulation hypothesis proposed by Schacter and Addis [17], as the ability to flexibly recombine details drawn from past experiences, own personal goals or events to construct an event that could plausibly occur in the near future. In this sense, it has been suggested that both remembering past and imagining future events are tightly related as they require the retrieval of information from memory, but imagining future scenarios could be considered a more demanding task because it entails the additional cognitive effort needed to recombine past memories in a plausible future situation involving the self [18]. Several studies demonstrated that EFT is affected by aging, in fact older people produce more semantic details and fewer internal episodic ones than younger people, both when they describe past events and—even more—when imagining the future [19, 20]. Often, when older adults have to imagine a future event, they simply recast past events in a future time, due to an age-related difficulty in recombining episodic details from various episodes [21]. Older adults also produce more emotional details than younger people [22]. These age-related differences in the qualities of people’s descriptions of past and future events have been accounted for in models of autobiographical memory [e.g., 23], which distinguish between the episodic component of autobiographical memory (which is affected by aging) and the semantic component, containing a more abstract autobiographical knowledge (which is preserved in aging) [19]. Being less able to create episodic details, particularly in the case of the more demanding future condition, older adults probably rely on semantic components of autobiographical memory to fill the gaps [22]. In view of these results, executive processes and working memory could play a role in explaining age differences in EFT. For example, it has been demonstrated, in young adults, that executive processes may support the strategic aspects of retrieving autobiographical details [24] and recombining them into future scenarios [25]. Among the various executive processes, Suddendorf and Corballis [26] have suggested that remembering past events and imagining future ones require a processing space where information is temporarily maintained and manipulated (i.e. WM). D’Argembeau et al. [25] examined in young adults the contribution of some executive function (verbal and semantic fluency) and working memory (measured with the
123
letter-number sequencing task taken from WAIS III, [27]) tasks to different dimension of episodic future thinking performance, i.e., fluency (e.g., how many unique future events can a person generate in 1 min), specificity (e.g., whether a person can construct a unique potential future event), and details (e.g., how many specific episodic details can a person produce about a possible future event). D’Argembeau et al. [25] reported that the factor representing executive processes was the only independent predictor of autobiographical fluency, autobiographical specificity, and the amount of episodic details. More recently, Hill and Emery [28] deepened the role of working memory for EFT, adapting the distinction made by D’Argembeau et al. [25] and presenting four measures of WM. Hill and Emery [28] demonstrated that the WM composite score was significantly correlated with future episodic specificity, over and above the relationship between future and past specificity. In contrast WM was not associated with the other EFT measures. Few studies examined this issue in older adults. For example Addis et al. [22] reported that the performance in the Digit backward span correlated with internal details produced, and this relationship was significant for future events. Another indirect suggestion of the relevance of executive processes and WM for EFT come from the study by Gaesser et al. [29] who showed that older adults performance decrease not only in imagination future events but also in picture description, and memory tasks; that appears to indicate that mechanisms other than episodic memory are also relevant to understanding EFT [see also 30]. On the basis of this short review of the existing data, the main goal of our study was to shed light on the underlying mechanisms that might explain EFT and the decrease of this ability in older adults. Based on the previous studies, we focused on WM and inhibition, which may plausibly be responsible for the declining recollection of specific past events and building of episodic future events with age. Since past events serve a directive function for EFT in a dynamic interaction, WM may bridge temporal discontinuities, integrating information from long-term memory stores with perceptual information for the purpose of episode generation in the past and future. Inhibition may also influence EFT performance, since it is believed to account for cognitive aging, and has been shown to mediate agerelated differences in WM. The role of these processes was assessed in a EFT task where a modified version of Galton’s classic paradigm, i.e., sentences reflecting common events, was used instead of cue words. This choice was driven by published data suggesting that people, and older adults especially, can produce more details if they are given more structured elements than single cue words [e.g., 31]. This may be because they are
Aging Clin Exp Res
facilitated in developing an episode with a consequently lower demand in terms of cognitive effort and resources. Consistently with this view, Levine et al. [32] showed that older adults could produce more episodic details in recalling past events when they are specifically probed to retrieve further details; under this condition, the proportion of episodic details increased in older adults, reducing the age effect seen in standard retrieval conditions (with no specific probe). A similar facilitating effect was observed in amnesic patients through the presentation of structured cue (i.e., scenarios that were explicit self-relevant and potentially plausible event in the future) both in remembering past events and in imaging future ones [33, 34]. In the current study, therefore, participants were cued with sentences about prototypical events (which may refer to script) in people’s lives, such as marriages, holidays, births, etc. Judging from the literature, we assumed that using sentences would help participants to generate specific episodic events, and this could apply particularly to older adults, especially when they have to imagine the future. We assessed age differences in events production in terms of their specificity (episodic vs. semantic details) vividness, emotional salience and importance to the young and older adults’ personal life, comparing past and future scenarios. In line with previous studies, we expected older adults to rate past events as more salient and relevant than future events. These analyses on the type of detail and the valence of the events described by participants [as proposed by 19–21, 25] enabled us to conduct a detailed quantitative analysis without neglecting the influence of subjective variables that could change with aging. A complementary goal was to analyze the effect of repetition of some cue sentences in both the past and the future condition. According to the episodic simulation hypothesis, because future events depend on the flexible recombination of details drawn from memory of past experiences, using the same cue in both conditions could make it easier to describe events (especially in the future) because they have already been activated by a previous presentation under the non-repeated condition. An opposite pattern of results could emerge, however. The use of sentences representing common situations and the repetition, due to a previous memory activation, might also lead to: (i) a greater production of stereotypic information unrelated to personal events; and (ii) a repetition of the same already-reported events.
Method
older adults (12 males and 24 females, mean age 62.11, SD 2.33). The younger adults were students or workers, while the older adults were workers or retired, and members of voluntary associations. All participants were Italian native speakers and volunteered for the study. None of them met the exclusion criteria proposed by Crook et al. [35] (i.e., a history of head trauma; any neurological or psychiatric illness; history of brain fever; dementia or any other state of altered consciousness; use of benzodiazepines in the last 3 months; use of illicit drugs; visual, auditory and/or motor impairment; any symptomatic cardiovascular conditions, breathing problems or diseases with the potential for causing cognitive impairments), or a Mini-Mental State score [36] below 27. The two age groups did not differ (p [ 0.05) in Wechsler Adult Intelligence Scale—revised (WAIS–R) vocabulary scores [37], or personal satisfaction scores on the Well-Being Questionnaire [38]. Older participants performed above the cutoff for their age and education in terms of vocabulary [Italian norms by 39], well-being (measured with the well-being questionnaire by 40) and WM (the Listening Span Test; see Italian norms, 40). The characteristics of the sample are summarized in Table 1.
Materials Autobiographical interview The stimuli consisted of 25 sentences representing common events1 (e.g., a christmas lunch, a dinner with colleagues); 10 were presented in the past condition, 10 in the future, and 5 in both. For each participant, the content of the sentences was randomly placed in the past or future, except for the five sentences repeated in both conditions, which were the same for all participants. The order of presentation of the past and future conditions was counterbalanced for each participant, so the repeated events were presented in the future for half of the participants (first in the past, then in the future condition), and in the past for the other half (first in the future, then in the past condition), in a counterbalanced fashion. Participants were encouraged to retrieve or imagine temporally and contextually specific events. Future events had to be plausible and both past and future events were not to span more than 1 day. Participants were asked to indicate the period in their life when the event
Participants The sample consisted of thirty-seven younger adults (17 males and 20 females, mean age 24.89, SD 2.33) and 36
1
The events were considered to be very common by three independent judges.
123
Aging Clin Exp Res Table 1 Characteristics [mean (M) and standard deviation (SD)] of participants by age group
Younger adults
Older adults
M
SD
M
SD
Age
24.89
2.33
62.11
2.33
Vocabulary
59.97
5.69
58.83
6.74
Well-being
32.43
3.74
32.58
4.23
Listening Span Test, words recalled correctly
30.22
4.68
23.42
5.91
0.02
0.03
0.09
0.09
Proportion of intrusions errors in the Listening Span Test
occurred or was expected to occur.2 The maximum time allowed to describe each episode was 3 min. For each sentence cue, participants qualitatively rated their past or future episode as suggested by D’Argembeau and Van der Linden [41] using a 5-point scale as follows: (a) relevance attributed to the episode (from 1: insignificant, irrelevant to my life, to 5: extremely relevant, a turning point in my life); (b) vividness of the episode (from 1: no image, I can only think about the situation, to 5: perfectly clear and as vivid as normal vision); (c) emotional importance of the episode (from 1: emotionally neutral, it arouses no emotion in me, to 5: extremely important, I have strong feelings about it). Scoring The qualities of participants’ recollections and simulations were estimated using an adapted version of the standardized scoring procedure developed by Levine et al. [32]. To be more precise, internal details (pertinent to the proposed sentence, and specific to the time and place) and external details (unassociated with the proposed sentence, semantic knowledge, repeated or unrealistic information) were identified for each past and future event that participants described. Listening Span Test (LST) [14] This task, originally devised by Daneman and Carpenter [42], consisted of sequences containing an increasing 2
Although all participants were asked to indicate the period in their life when the event occurred or was expected to occur, data recording was available for a limited number of participants (30 young adults; 13 older adults). The tendency emerging from available data was explored with a 2 (young vs. old) by 2 (past vs. future) ANOVA on the number of years reported for past events and future events. Results showed a significant Age x Condition interaction, F(1,41) = 7.44, p \ 0.01 g2p = 0.15: older adults (M 14.71, SD 8.42) rated their past events as having occurred a longer time before than young adults (M 6.38, SD 3.21). Moreover, only older adults reported events in the past as being more remote from the present than was the case for events imagined in the future (p = 0.004). No age-related differences were found for the future condition (young adults: M 6.84, SD 7.23; older adults: M 6.26, SD 8.28). Age-related differences in the time elapsing between the event and the present were only seen for past events.
123
number (from 2 to 6) of simple sentences. The sequences of sentences were grouped into four sets of four sequences. Twenty sentences were presented in each set (giving a total of 80 sentences), with an interval of 1.5 s between one sentence and the next. Participants were asked to listen to each sentence, judge its plausibility (i.e., say whether it was true or false) and retain the last word. At the end of each set of sentences, participants had to recall the last words of all the sentences in their order of presentation. The task was preceded by two practice trials. The total number of final words correctly recalled during the test was considered the measure of the individuals’ WM capacity. Intrusion errors (i.e., words recalled that were contained in the sentences but were not final words) were also computed. The purpose of this procedure was to measure the individuals’ ability to exhibit control over the permanence of information in their WM [e.g., 14, 43], i.e., inhibitory control. Procedure The experiment was conducted in two sessions taking 2.5 h altogether. The health history interview was conducted in the first session, when the core part of the study was also introduced, explaining the notion of mental imagery, with examples of imagining future and recalling past events. Then the sentences were presented and the participants’ descriptions of events were recorded. The Well-Being questionnaire [38] was administered in between the presentation of the sentences in the two temporal conditions (past and future) to avoid any facilitation effects of the former condition on the latter. The second session was dedicated to the Listening Span Test [40] and the Vocabulary subtest [WAIS-R, 37]. Transcripts of participants’ descriptions were subsequently segmented into various categories by two trained raters, who were unaware of the study hypotheses. Using Cohen’s kappa (K), inter-rater agreement for scoring of internal and external details was high ([0.90).
Aging Clin Exp Res
Results Processing resources: WM and inhibition To assess age-related differences in WM capacity and inhibition, two separate one-way ANOVA were run on: (i) the number of words correctly recalled in the Listening Span Test; and (ii) the proportion of intrusion errors in the Listening Span Test, i.e., the number of intrusions errors/ number of correct items recalled (see Table 1 for descriptive statistics). Working memory task Our results for the number of words recalled correctly in the Listening Span Test showed a main effect of group, F(1,71) = 35.89, p \ 0.001, g2p = 0.34; the young adults recalled more words than the older adults (MDiff. = 7.30, p \ 0.001) (see Table 1). Intrusion errors-inhibitory measure There was a significant main effect of Group on the proportion of intrusion errors in the Listening Span Test, F(1,71) = 19.31, p \ 0.001, g2p = 0.21: the older adults produced a higher proportion of intrusion errors than their younger counterparts (MDiff. = 0.08, p \ 0.001) (see Table 1).
and condition (past vs. future) for the repeated measures, on: (i) the relevance of the events described; (ii) the vividness of the events described in response to the sentences; (iii) the emotional importance of the events described in the past and in the future. For all the analyses, the interactions were broken down using post hoc pairwise comparisons with Bonferroni’s correction at p \ 0.05, adjusted for multiple comparisons. Mean number of internal and external details For the internal details (see Table 2), the results showed that the main effect of Group was significant, F(1,71) = 17.67 p \ 0.001 g2p = 0.20, indicating that young adults produced more details than older adults (MDiff. = 6.29, p \ 0.001). The main effect of Condition was also significant, F(1,71) = 43.06 p \ 0.001 g2p = 0.38: more details were given for past than for future events (MDiff. = 6.25, p \ 0.001). The Group 9 Condition interaction was not significant, however, F \ 1. For external details, the results showed the main significant effect of Group, F(1,71) = 5.00 p \ 0.05 g2p = 0.07, indicating that young adults produced less external details than older adults (MDiff. = -0.98, p \ 0.001. No other significant effects emerged: condition F \ 1; group 9 condition F \ 1 (see Table 2). The effect of repetition on internal and external details
Autobiographical interview First, the mean number of details produced by participants was analyzed using two separate repeated measures ANOVA on internal and external details, with Group (young, older adults) as a between-subjects factor and Condition (past or future) as a within-subject factor. This was done because the range for the details differed considerably between the two categories (the range for internal details was from 10 to 50, while for external details it was from 0 to 10). Second, the effect of repetition on the production of events in the past and future was analyzed, again distinguishing between internal and external details. Two separate ANOVA were run on internal and external details, one for the past condition and the other for the future one, with Group (young, older adults) as a between-subjects factor and repetition (repeated vs. non-repeated) as a within-subject factor. A separate analysis was necessary because half of the participants were presented with repeated sentences in the past, the other half with repeated sentences in the future, using a counterbalanced method. A series of repeated-measures ANOVA were run, with group (young vs. older adults) as a between-subjects factor,
Analyzing the mean number of internal details for repeated sentences in the past condition, our results showed that the main effect of Group, F \ 1, and the Group 9 Repetition interaction, F(1,35) = 2.50 p = 0.12 g2p = 0.07, were not significant. On the other hand, the main effect of Repetition was significant, F(1,35) = 6.53 p \ 0.05 g2p = 0.16, more internal details being given for repeated than for non-repeated sentences (MDiff. = 2.33, p \ 0.05) (see Table 2).
Table 2 Mean number of internal and external details in sentences presented only once or repeated, by condition (past vs. future) and age group Younger adults
Older adults
M
SD
M
SD
27.46 1.39
9.82 1.50
21.96 2.10
6.66 2.85
Internal
22.00
8.74
14.91
3.33
External
0.98
1.50
2.22
2.62
Past Internal External Future
123
Aging Clin Exp Res
When the repeated sentences were presented in the future condition, we found a main effect of Group, F(1,34) = 6.25 p \ 0.05 g2p = 0.16, indicating that the younger adults included more internal details than older adults (MDiff. = 7.16, p \ 0.05). The main effect of Repetition, F(1,34) = 2.19 p = 0.15 g2p = 0.06, and the Group 9 Repetition interaction, F(1,34) = 2.66 p = 0.11 g2p = 0.07, were not significant. The results for external details revealed no significant differences (F \ 1) when repeated sentences were presented in the past condition. Instead, when the effect of repetition in the future was analyzed, the results showed a significant Group x Repetition interaction, F(1,34) = 7.81 p \ 0.01 g2p = 0.19, indicating that younger adults included more external details for repeated than for nonrepeated sentences (p = 0.011). No other effects were found (F \ 1) (see Table 2). Relevance of the events produced The main effects of Group and Condition were not significant (F \ 1), but the Group x Condition interaction was significant, F(1,71) = 10.71 p \ 0.01 g2p = 0.14, and indicated that the young adults considered imagined events (future condition) more significant (MDiff. = 0.22, p = 0.008) than those remembered from their past (see Table 3). Vividness of the events described The main effect of Group, F(1,71) = 2.46 p [ 0.05 g2p = 0.03, and the Group x Condition interaction, F(1,71) = 1.86 p = 0.18 g2p = 0.03, were not significant, but the main effect of Condition was significant, F(1,71) = 31.29 p \ 0.001 g2p = 0.31, indicating that events from the past generated more vivid mental images than those set in the future (MDiff. = 0.33, p \ 0.001) (see Table 3). Table 3 Mean value (1–5 Likert scale) of vividness, and emotional salience attributed to past and future events by age group Younger adults M
Older adults SD
M
SD
Relevance Past
2.89
0.43
3.13
0.44
Future
3.11
0.53
2.96
0.54
Vividness Past
3.83
0.52
3.74
0.45
Future
3.59
0.67
3.33
0.49
Salience Past
3.00
0.53
3.34
0.41
Future
3.25
0.54
3.11
0.52
123
Emotional importance of the events described The main effects of Group and Condition were not significant (F \ 1 for both). The Group x Condition interaction was significant, F(1,71) = 16.82 p \ 0.001 g2p = 0.19: in the past condition, events were rated as more salient by the older than by the younger adults (p = 0.004), whereas in the future condition, there were no significant differences between the two groups. The younger adults rated imagined events as more emotionally salient than remembered ones (p = 0.003), while the older adults rated remembered events as having a greater emotional charge than imagined ones (p = 0.008) (see Table 3). Correlations Correlation analyses (see Table 4) were conducted to enable a preliminary assessment of the relationship between age, type of detail (internal, external) in response to sentences used in the past or future conditions, and participants’ performance in the Listening Span Test, i.e., words correctly remembered (which is a measure of WM capacity) and proportion of intrusion errors (which is an indicator of inhibitory control-inhibitory mechanisms). As expected, our findings showed a negative correlation between age and internal details, which was large [according to 44] for the future condition (r = -0.59), but small for the past (r = -0.30). Age also correlated negatively with processing resources (WM r = -0.59), and inhibitory mechanisms (r = 0.49), consistently with the literature [45]. A small correlation was found between age and external details, however, but only in the past (r = 0.28). The mean number of internal details reported for past events correlated moderately with the number of internal details reported in the future condition (r = 0.51), and of external ones in the past with those in the future (r = 0.46) in line with the episodic simulation hypothesis. In both conditions, the mean number of internal details also correlated with WM performance (r = 0.30 and r = 0.33, for the past and future, respectively), while a small negative correlation emerged between the proportion of internal details in the future and the errors in the WM task (r = -0.32), suggesting that participants who produced more internal details in the future had more efficient inhibitory mechanisms too. Since the aim of our analysis was exploratory; however, these correlations should be interpreted with caution because no corrections were applied. Regression analyses Hierarchical regression analyses were run to estimate the percentage of variance for the internal and external details
Aging Clin Exp Res Table 4 Correlations between age, details (internal, external) generated in response to sentences presented only in past or future conditions, working memory (Listening Span Test), and inhibition (intrusion errors in the Listening Span Test) 1
2
3
4
5
6
Age Past internal details
-0.30*
Future internal details
-0.50**
0.51**
Past external details
0.28*
0.27*
0.02
Future external details
0.17
0.22
0.10
-0.59**
0.30*
0.33**
-0.09
-0.01
-0.32**
0.37
0.06
Listening Span Test, words recalled correctly Proportion of intrusions errors in the Listening Span Test
0.49**
-0.11
0.46** -0.47**
N = 73 LST listening span test * p \ 0.05; ** p \ 0.01
produced (criterion variables), which was explained by age and processing resources (WM, inhibition), and the same type of detail (internal or external) being produced in the other temporal condition (i.e., the dependent variable was internal details in the future when the past condition was analyzed, and internal details in the past when the future condition was considered). Two different models were used, which differed in the order of the variables entered, to assess the role of age vs. cognitive resources and details in either temporal condition; the latter predictors were regressed before and after the age variable. In Model 1, age was entered in step 1. WM, inhibition and internal details in the future (when the criterion variable was internal details in the past), or in the past (when the criterion variable was internal details in the future) were entered in Step 2. In Model 2, the order of entry of the variables was: WM and inhibition and internal details (step 1), and age (step 2). Cook’s distance was computed to detect outliers (cook’s distance [1) on the criterion and predictor variables, but none were found. Nor did the variance inflation factors or tolerance criteria indicate any significant multicollinearity [45]. For the internal details given in the past condition, Model 1 showed that age explained a significant part of the variance (R2 = 0.09, p \ 0.01), while processing resources and internal details in the future condition (step 2) contributed to explaining an additional 6.7 % of the variance; the internal details in the future conditions (b = 0.49, p \ 0.001) was the unique salient predictors. When age was entered in the last step, however (Model 2), only processing resources and internal details explained a significant part of the variance (R2 = 0.30, p \ 0.001), while age was no longer a significant predictor. In fact, the mean number of internal details in the future conditions (b = 0.49, p \ 0.001) made a unique contribution to the variance explained.
As for the internal details produced in the future condition, Model 1 showed that age explained a significant part of the variance in step 1 (R2 = 0.25, p \ 0.001), while processing resources and internal details in the past condition (step 2) contributed to explaining an additional 6.1 % of the variance; age (b = -0.35, p \ 0.01) and the mean number of internal details in the future conditions (b = 0.42, p \ 0.001) were the unique salient predictors. Model 2 showed the same results, in fact processing resources and internal details in the past (Step 1) explained a significant part of the variance (R2 = 0.34, p \ 0.001), and age (Step 2) explaining an additional 8 % of variance: Age (b = -0.35, p \ 0.01) and the mean number of internal details in the future conditions (b = 0.42, p \ 0.001) were the unique salient predictors. When we looked at the external details produced in the past condition, Models 1 and 2 both showed that only processing resources and external details in the future condition explained a significant part of variance (Model 1, R2 = 0.24, p \ 0.01; Model 2, R2 = 0.23, p \ 0.01). The mean number of external details in the future conditions (b = 0.49, p \ 0.001) was the unique salient predictors. Finally, when it came to external details produced in the future condition, Model 1 showed that age explained a significant part of variance (R2 = 0.08, p \ 0.05), processing resources and external details in the past (Step 2) explained an additional 9.2 % of variance. Intrusion errors in Listening Span Test (b = 0.35, p \ 0.01) and the mean number of external details in the past conditions (b = 0.42, p \ 0.001) were the unique salient predictors. Model 2 showed that only processing resources and external details in the past (step 1) explained a significant part of variance (R2 = 0.33, p \ 0.05); intrusion errors (b = 0.38, p \ 0.01) and the mean number of external details in the past (b = 0.44, p \ 0.001) were the unique salient predictors. Overall, these results show that, while for internal details only age and internal details in the other condition
123
Aging Clin Exp Res
explaining the variance, for the external details the role of the predictors changed, depending on whether the past or future condition was considered. In the past condition, only the number of external details in the future condition contributed to the variance explained for internal details; in the future condition age and processing resource, in particular inhibition, accounted for the variance in the production of internal details imagined in the future. Comparison between the use of contextual information vs. specific cues in EFT In Table 5, we qualitatively compare the results, in terms of age-related differences, between the present study, in which contextual information (as provided by sentences) is used, and other studies adopting other procedures (words, or pictures as cues). The use of contextual information appears to advantage older adults with respect to the percentage of internal details.
Discussion The main goal of our study was to shed light on the EFT phenomenon, understanding the role of age and some processing resources (WM and inhibition) that are particularly sensitive to aging [45], since no previous studies addressed the influence of processing resources on EFT. Our results showed that internal details produced in the other experimental (future or past) condition and age influence internal details produced in the past and in the future condition. Further, and more interestingly, we found that only for the production of external details, the role of age and processing resources change depending on whether the past or future condition was involved. In fact, processing resources and the external details produced in the other experimental condition (that is in the future condition), predicted the mean number of external details produced in the past condition, on the one hand. On the other hand, age and inhibition explained external details produced in the future condition. Such a result suggests that, with aging, there is an increase in the external details produced and this appears to be related to the decrease in Table 5 Summary of the percentage of internal details produced, in remembered or imagined events, in different cueing conditions by age group (published in peer-reviewed journals)
123
References
the efficiency of inhibitory mechanisms. Further, because of the decline in inhibitory mechanisms, older people may have more difficulty in pursuing the goal of describing specific episodes, and this could cause the increase of irrelevant and semantic details. Moreover, these findings suggest that the nature of the close relationship between remembering the past and imagining the future is multidimensional. They also confirm that cognitive abilities that decline with age, such as WM and inhibition [7], may contribute to EFT performance [25]. Future studies should strive to adopt a multivariate design that includes other cognitive measures in order to shed light on EFT in aging. Regarding the assessment of age-related differences in the specificity and the subjective quality (relevance to the individuals’ personal life, vividness of the mental image, and emotional salience) of events produced in past and future conditions a modified version of the classic Galton paradigm was used (i.e., we used sentence cues instead of words). We felt that using sentence cues representing common life events might facilitate participants’ access to their personal autobiographical information and thus help them to bind episodic knowledge with possible future scenarios, especially for older adults [e.g. 32–34]. Some of the sentences were also presented in both past and future conditions; this permitted us to assess the presence of a facilitator effect to pre-activate episodic information that could be recombined to construct new episodes or to recall past episodes, particularly for older adults. The events produced in the past and future were broken down into internal and external details, and were rated qualitatively by the participants, as suggested by D’Argembeau and Van der Linden [41]. When we considered the mean number of internal details, all participants produced more details in the past than in the future condition, and younger adults produced more details than older adults. No age-related differences emerged in the mean number of external details produced. These results extend available data on the age-related reduction in episodic specificity for past events [32, 46] and show that contextual information (as provided by sentences) enables older adults to produce more on-task information than when the classic procedure is used, or more
Type of cue
Past Young (%)
Future Old (%)
Youn (%)
Old (%)
Current study
Sentences
94
92
94
87
Gaesser et al. [29]
Pictures
*84
*67
*87
*66
Addis et al. [21]
Personalized memory cue
*76
*60
*69
*55
Gamboz et al. [53]
Words
_
*69
_
*67
Addis et al. [22]
Words
*84
*56
*68
*51
Aging Clin Exp Res
specific cues [21, 29], as in previous studies (see Table 5). The benefit of contextual cues is also suggested by the fact that the mean number of semantic details produced did not differ between the two age groups, neither in the past nor in the future condition. A qualitative comparison with previous studies (see Table 5) showed that the percentage of internal details produced by our group of older adults was higher than in other, more facilitating cueing conditions— involving the use of pictures and personalized memory cues, for instance [21, 29]. Nevertheless, our results showed that age-related differences were still significant, particularly when the future condition was considered. Our use of repetition, involving some sentences being presented in both past and future conditions, also always had a beneficial effect when internal details were considered: repeating the same sentences in the past nullified any age-related differences, with all participants producing more internal details in the repeated than in the non-repeated sentences. Older adults were thus able to produce as many details as young adults (see Table 2). In line with our hypotheses, this pattern of findings suggests that using the same cue in both conditions favors the retrieval of internal details of events that have already been activated with the previous presentation (under the non-repeated condition), or may provide older adults with a sort of environmental support [47]. On the other hand, the use of repeated sentences in the future conditions did not influence the agerelated differences in the production of internal details, since younger adults continued to outperform elders. The use of sentences and their repetition, when participants are asked to remember past events at least, therefore, facilitate the production of autobiographical details, suggesting that the ability to do so depends on the type of cue used, and on its activation. As for external details, age-related differences were no more significant in the past and future condition. Repeating the sentences yielded the production of a higher rate of external details in the younger group, however, probably due to some interference effects. With respect to the quality of the descriptions of events, the older adults attributed more relevance and emotional salience to episodes in the past, probably because they tended to reinterpret their past in a more positive light [48]. This may also explain the non-significant difference between the two age groups when internal details for past events were examined, confirming that age-related differences are reduced or nullified when the information has some personal relevance or emotional valence for older adults [see 49]. In fact, there are a number of studies showing that older adults perform as well as younger when valenced material (i.e., affective stimuli such as positive pictures are used—the so-called positivity bias with aging) is presented [50]: the greater motivated tendency to focus
on positive stimuli may help reducing their cognitive difficulties typically shown with neutral material [51]. It would, therefore, be of interest to examine EFT using emotional stimuli as cues as well. In contrast, younger people see their future as more important and are more optimistic about it [52, 53]. This might partly explain the younger adults’ better performance in imagining future events. Younger people tend to structure their future around personal goals [54] and this seems to prompt a greater use of episodic details to describe future events [55]. On the other hand, participants in both age groups rated their mental images of possible future events as being less vivid than their memories—as expected—probably because future events are characterized by fewer contextual and sensory details than past events [56]. This impression is also supported by the fact that age-related differences were not significant when participants were asked to indicate when the event could occur in the future. This is just one possible interpretation, however, given the data recording problems relating to this aspect (see note 2). Despite our insightful results, the present study has some limitations that need to be mentioned, such as the fact that we did not include the classical use of word cues to elicit events and thereby draw a direct comparison with the benefits of using sentence cues emerging from our results. Our qualitative comparison conducted with previous studies nonetheless suggests that using sentence cues is a promising approach to the study of EFT. Future studies could thus try to use different types of cue to replicate and clarify the present findings. Further, it would be of interest to assess whether presenting sentences instead of words as cues helps people to imagine future scenarios as well as to recall past events (as the greater detail produced by participants in this study in response to sentences instead of word cues seems to suggest), or whether sentence cues favor the production of prototypical events instead. Our study design also meant that we could not establish whether or not the effect of repeating cues remained the same if they were repeated after being presented first in the past or in the future condition. In addition, no old–old group was considered in this study, which might have shed some light on how very old age influences the pattern of results described here. To sum up, our study shows that older adults produce less episodic information than younger people, whether they are remembering the past or imagining future events, and they tend to compensate by producing more semantic information. The present results highlight also the importance of considering also qualitative differences between young and older adults: age-related differences in narrative style and in the relevance personally attributed to events appear to explain older adults’ different performance in
123
Aging Clin Exp Res
remembering past and imagining future events. Further, the different involvement of processing resources in EFT casts light on the differences between the production of internal and external episodes in aging. Finally, the role of type of material used to elicit EFT, should be taken into account as a potential crucial variable, as using sentence cues, and repeating them, appears to facilitate older adults’ production of internal details, nullifying the above-mentioned age-related differences when they have to remember a past event. Acknowledgments The authors wish to thank Irene Grasso for helping in data processing. This work was supported by a grant from the Italian Ministry of Research and Education (Progetto PRIN: 2010P8LRP7_003). Conflict of interest
None.
Human and Animal Rights The study was conducted according to standards derived from the Declaration of Helsinki. Informed consent A written informed consent was obtained from every patient.
References 1. Kray J, Lindenberger U (2000) Adult age differences in task switching. Psychol Aging 15(1):126–147 2. Craik FIM, Bialystok E (eds) (2006) Lifespan cognition: Mechanisms of change. Oxford University Press, Oxford, pp 297–314 3. Salthouse TA (1990) Working memory as a processing resource in cognitive aging. Dev Rev 10(1):101–124 4. Daigneault S, Braun CM (1993) Working memory and the selfordered pointing task: further evidence of early prefrontal decline in normal aging. J Clin Exp Neuropsyc 15(6):881 5. Park DC, Lautenschlager G, Hedden T et al (2002) Models of visuospatial and verbal memory across the adult life span. Psychol Aging 17:299–320 6. Bopp KL, Verhaeghen P (2005) Aging and verbal memory span: a meta-analysis. J Gerontol B Psychol Sci Soc Sci 60:223–233 7. Hasher L, Zacks RT (1988) Working memory, comprehension, and aging: a review and a new view. Psychol Learn Motiv 22:193–225 8. Verhaeghen P, De Meersman L (1998) Aging and the stroop effect: a meta-analysis. Psychol Aging 13(1):120–126 9. Langenecker SA, Nielson KA, Rao SM (2004) fMRI of healthy older adults during stroop interference. Neuroimage 21(1):192–200 10. Hasher L, Lustig C, Zacks RT (2007) Inhibitory mechanisms and the control of attention. In: Conway A, Jarrold C, Kane M, Miyake A, Towse J (eds) Variation in working memory. Oxford University Press, New York, pp 227–249 11. Belanger S, Belleville S (2009) Semantic inhibition impairment in mild cognitive impairment: a distinctive feature of upcoming cognitive decline? Neuropsychology 23(5):592 12. Borella E, Delaloye C, Lecerf T et al (2009) Do age differences between young and older adults in inhibitory tasks depend on the degree of activation of information? Eur J Cogn Psychol 21(2):445–472
123
13. Harnishfeger KK, Bjorklund DF (1993) The ontogeny of inhibition mechanisms: A renewed approach to cognitive development. In: Howe ML, Pasnek R (eds) Emerging themes in cognitive development, vol 1. Springer-Verlag, New York 14. Borella E, Carretti B, De Beni R (2008) Working memory and inhibition across the adult life-span. Acta Psychol 128:33–44 15. Hamm VP, Hasher L (1992) Age and the availability of inferences. Psychol Aging 7:56–64 16. Craik FIM, Salthouse TA (eds) (2000) Handbook of aging and cognition, 2nd edn. Lawrence Erlbaum Associates, Hillsdale 17. Schacter DL, Addis DR (2007) The cognitive neuroscience of constructive memory: remembering the past and imagining the future. Philos T R Soc B 362:773–786 18. Addis DR, Pan L, Vu MA, Laiser N, Schacter DL (2009) Constructive episodic simulation of the future and the past: distinct subsystems of a core brain network mediate imagining and remembering. Neuropsychologia 47:222–238 19. Gamboz N, Brandimonte MA, De Vito S (2010) The role of past in the simulation of autobiographical future episodes. Exp Psychol 57:419–428 20. Gamboz N, De Vito S, Brandimonte MA et al (2010) Episodic future thinking in amnesic mild cognitive impairment. Neuropsychologia 48:2091–2107 21. Addis DR, Musicaro R, Pan L, Schacter DL (2010) Episodic simulation of past and future events in older adults: evidence from an experimental recombination task. Psychol Aging 25:369–376 22. Addis DR, Wong AT, Schacter DL (2008) Age-related changes in the episodic simulation of future events. Psychol Sci 19:33–41 23. Conway MA (2001) Sensory-perceptual episodic memory and its context: autobiographical memory. Philos T R Soc B 356:1375–1384 24. Rubin DC (2006) The basic-systems model of episodic memory. Perspect Psychol Sci 1:277–311 25. D’Argembeau A, Ortoleva C, Jumentier S et al (2010) Component processes underlying future thinking. Mem Cogn 38:809–819 26. Suddendorf T, Corballis MC (2007) The evolution of foresight: what is mental time travel, and is it unique to humans? Behav Brain Sci 30(3):299 27. Wechsler D (2000) Echelle d’intelligence pour adulte, 3rd edn. Editions du, Paris 28. Hill P, Emery LJ (2013) Episodic future thought: contributions from working memory. Conscious Cogn 22(3):677 29. Gaesser B, Sacchetti DC, Addis DR, Schacter DL (2011) Characterizing age-related changes in remembering the past and imagining the future. Psychol Aging 26:80–84 30. Squire L et al (2010) Role of the hippocampus in remembering the past and imagining the future. Proc Natl Acad Sci USA 107(44):19044 31. Zacks RT, Hasher L, Li KZH (2000) Human memory. In: Salthouse TA, Craik FIM (eds) Handbook of aging and cognition. Lawrence Erlbaum Associates, Mahwah 32. Levine B, Svoboda E, Hay JF et al (2002) Aging and autobiographical memory: dissociating episodic from semantic retrieval. Psychol Aging 17:677–689 33. Hurley N, Maguire EA, Vargha-Khadem F (2011) Patient HC with developmental amnesia can construct future scenarios. Neuropsychologia 49(13):3620 34. Race E, Keane MM, Verfaellie M (2011) Medial temporal lobe damage causes deficits in episodic memory and episodic future thinking not attributable to deficits in narrative construction. J Neurosci 31(28):10262–10269 35. Crook T, Bartus RT, Ferris SH et al (1986) Age associated memory impairment: proposed diagnostic criteria and measures
Aging Clin Exp Res
36.
37. 38.
39.
40.
41.
42. 43.
44. 45.
of clinical change-report of a national institute of mental health work group. Dev Neuropsychol 2:261–276 Folstein MF, Folstein SE, McHugh PR (1975) ‘‘Mini-mental state’’: a practical method for grading the cognitive state of patients for the clinician. J Psychiat Res 12:189–198 Wechsler D (1981) Wechsler adult intelligence scale-revised manual. The Psychological Corporation, New York De Beni R, Marigo C, Nava LA et al (2008) BEN-SSC. Benessere e invecchiamento, in De Beni, Borella, Carretti, Marigo e Nava, pp. 97–114 Orsini A, Laicardi C (2003) Wais-R e terza eta`. La natura dell’intelligenza nell’anziano: continuita` e discontinuita`. [WAISR and the third age. The nature of intelligence in elderly people: continuity and discontinuity]. Firenze, Giunti OS De Beni R, Borella E, Carretti B, et al (2008) BAC. Portfolio per la valutazione del benessere e delle abilita` cognitive nell’eta` adulta e avanzata [The assessment of well-being and cognitive abilities in adulthood and aging]. Firenze, Giunti OS D’Argembeau A, Van der Linden M (2004) Phenomenal characteristics associated with projecting oneself back into the past and forward into the future: influence of valence and temporal distance. Conscious Cogn 13:844–858 Daneman M, Carpenter PA (1980) Individual differences in working memory and reading. J Verb Learn Verb Be 19:450–466 De Beni R, Palladino P, Pazzaglia F et al (1998) Increases in intrusion errors and working memory deficit of poor comprehenders. Q J Exp Psychol A 51:305–320 Cohen J (1988) Statistical power analysis for the behavioral sciences. Lawrence Erlbaum, Hillsdale Borella E, Ghisletta P, de Ribaupierre A (2011) Age differences in text processing: the role of working memory, inhibition and processing speed. J Gerontol B Psychol Sci Soc Sci 66:311–320
46. De Beni R, Palladino P (2004) Decline in working memory updating through ageing: intrusion error analyses. Memory 12:7589 47. Craik FIM, Byrd M (1982) Aging and cognitive deficits: the role of attentional resources. In: Craik FIM, Trehub S (eds) Aging and cognitive processes. Plenum, New York, pp 191–211 48. Carstensen LL (2006) The influence of a sense of time on human development. Science 312:1913–1915 49. Mammarella N, Borella E, Carretti B et al (2013) Assessing affective working memory: evidence from age-related differences. Neuropsychol Rehabil 23(3):1–13 50. Mikels JA, Larkin GR, Reuter-Lorenz PA et al (2005) Divergent trajectories in the aging mind: changes in working memory for affective vs. visual information with age. Psychol Aging 20:542–553 51. Dolcos F, LaBar KS, Cabeza R (2004) Dissociable effects of arousal and valence on prefrontal activity indexing emotional evaluation and subsequent memory: an event-related fMRI study. Neuroimage 23:64–74 52. D’Argembeau A, Van der Linden M (2006) Individual differences in the phenomenology of mental time travel: the effect of vivid visual imagery and emotion regulation strategies. Conscious Cogn 15:342–350 53. Gamboz N, De Vito S, Brandimonte MA et al (2010) Episodic future thinking in amnesic mild cognitive impairment. Neuropsychologia 48(7):2091–2097 54. Austin JT, Vancouver JB (1996) Goal constructs in psychology: structure, process, and content. Psychol Bull 120:338–375 55. D’Argembeau A, Mathy A (2011) Tracking the construction of episodic future thoughts. J Exp Psychol 140:258–271 56. Szpunar KK (2010) Episodic future thought: an emerging concept. Perspect Psychol Sci 5:142–162
123
