Research in Developmental Disabilities 35 (2014) 261–268
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Research in Developmental Disabilities
Emotional false memories in children with learning disabilities Chiara Mirandola a,*, Nunzia Losito a, Simona Ghetti b, Cesare Cornoldi a a b
Department of General Psychology, University of Padova, Italy Department of Psychology and Center for Mind and Brain, University of California, Davis, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 25 August 2013 Received in revised form 5 November 2013 Accepted 6 November 2013 Available online 30 November 2013
Research has shown that children with learning disabilities (LD) are less prone to evince associative illusions of memory as a result of impairments in their ability to engage in semantic processing. However, it is unclear whether this observation is true for scripted life events, especially if they include emotional content, or across a broad spectrum of learning disabilities. The present study addressed these issues by assessing recognition memory for script-like information in children with nonverbal learning disability (NLD), children with dyslexia, and typically developing children (N = 51). Participants viewed photographs about 8 common events (e.g., family dinner), and embedded in each episode was either a negative or a neutral consequence of an unseen action. Children’s memory was then tested on a yes/no recognition task that included old and new photographs. Results showed that the three groups performed similarly in recognizing target photographs, but exhibited differences in memory errors. Compared to other groups, children with NLD were more likely to falsely recognize photographs that depicted an unseen cause of an emotional seen event and associated more ‘‘Remember’’ responses to these errors. Children with dyslexia were equally likely to falsely recognize both unseen causes of seen photographs and photographs generally consistent with the script, whereas the other participant groups were more likely to falsely recognize unseen causes rather than script-consistent distractors. Results are interpreted in terms of mechanisms underlying false memories’ formation in different clinical populations of children with LD. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Specific learning disabilities False memories Emotional content
1. Introduction Memory illusions occur quite frequently in the laboratory as well as in real life, and their developmental trajectory depends on the nature of the illusion. When memory illusions stem from processing semantically related information (e.g., Deese–Roediger–McDermott (DRM) paradigm: Brainerd, Holliday, & Reyna, 2004; connected–meaning paradigms: Howe, 2006), typically developing children often demonstrate age-related increases in the frequency of memory errors (Brainerd, Reyna, & Ceci, 2008; Brainerd, Reyna, & Zember, 2011; but see Ghetti, Qin, & Goodman, 2002; Lampinen, Leding, Reed, & Odegard, 2006). The DRM paradigm involves the presentation of several lists of semantically related words (e.g., sick, nurse, medicine). Within each list, all words are associated to a single word not presented during encoding, the critical lure (in this
* Corresponding author at: Department of General Psychology, University of Padova, Via Venezia 8, 35131 Padova, Italy. Tel.: +39 049 827 6617; fax: +39 049 827 6600. E-mail address: [email protected] (C. Mirandola). 0891-4222/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ridd.2013.11.004
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example, doctor). At retrieval, adults and older children falsely recognize the critical lures almost at the same rate as target words. Younger children recognize the critical lures to a lesser extent than older children and adults, thus committing fewer memory errors. This developmental trend persists even when emotionally charged stimuli are used instead of neutral stimuli (Brainerd, Holliday, Reyna, Yang, & Toglia, 2010; Howe, 2007; Howe, Candel, Otgaar, Malone, & Wimmer, 2010, Experiment 2). However, it is unclear to what extent these observed trends may apply to memory for life events, as well as to special clinical populations. Most of the available research on false memory formation in certain clinical populations of children primarily focuses on the implication of eyewitness memory or suggestibility in maltreated children (Howe, Cicchetti, Toth, & Cerrito, 2004), children within autism spectrum disorders (McCrory, Henry, & Happe`, 2007), or other severe developmental disabilities, such as intellectual disabilities (Brown, Lewis, Lamb, & Stephens, 2012; Henry & Gudjonsson, 1999, 2004; Young, Powell, & Dudgeon, 2003). The majority of these studies are aimed at evaluating the best way to administer a cognitive interview when children are either victims or witnesses of abuse and are required to provide allegations in the courtroom. However, little is known about the functioning of basic underlying memory processes in these populations. Furthermore, only a few studies have investigated memory accuracy and memory distortions in special populations of children with academic difficulties, such as children with reading comprehension difficulty (Mirandola, Del Prete, Ghetti, & Cornoldi, 2011; Weekes, Hamilton, Oakhill, & Holliday, 2008), children with attention deficit/hyperactivity disorder (ADHD; Mirandola, Paparella, Re, Ghetti, & Cornoldi, 2012), and children with general learning disabilities (Brainerd, Forrest, Karibian, & Reyna, 2006). Research conducted with the DRM paradigm (Roediger & McDermott, 1995) has shown that children with learning disabilities produce fewer memory errors than typically developing children (Brainerd et al., 2006; Weekes et al., 2008). This result has been associated with lower semantic processing abilities that prevent children with disabilities from relying on the gist of the wordlists, thus mimicking the pattern of errors found when comparing younger to older children. It must be noted that these studies focused specifically on memory errors, and it is unclear whether semantic processing difficulties associated with learning disabilities may influence the way in which children retain correct information as well. A paradigm specifically designed to investigate recognition memory and text-based detail recollection in adolescents with poor semantic text processing ability revealed an overall impaired recognition of sentences and related recollection (i.e., lower proportion of Remember judgments in association with correctly recognized target sentences) in these students, compared to a control group, despite both groups displaying similar recognition memory for isolated words (Mirandola et al., 2011). The present study was designed to investigate memory accuracy and errors in two distinct groups of children with learning disabilities, namely children with nonverbal learning disability (NLD) and children with dyslexia. Children with dyslexia are characterized by poor reading decoding abilities and sometimes show reduced semantic processing abilities (Betjemann & Keenan, 2008), as confirmed by recent studies combining fMRI and ERPs (Schulz et al., 2008, 2009). Whereas children with dyslexia present both language and reading skills impairments, children with NLD have good verbal skills, but a neuropsychological profile characterized by impairments in nonverbal abilities (Rourke, 1995). One of the identifying features of NLD is a significantly higher performance on tasks measuring verbal intelligence than on those measuring visuospatial intelligence (Cornoldi, Venneri, Marconato, Molin, & Montinari, 2003; Johnson, 1987; Mammarella et al., 2009; Weintraub & Mesulam, 1983). A factor underlying this discrepancy is that children with NLD possess poor visuospatial and visuoconstructive abilities, which would explain their difficulties in a broad range of school and everyday life activities including, but not limited to, mathematics, drawing, and spatial orientation (Cornoldi, Dalla Vecchia, & Tressoldi, 1995; Cornoldi, Rigoni, Tressoldi, & Vio, 1999; Cornoldi & Vecchi, 2003; Mammarella & Cornoldi, 2005). Most important for the current purposes, children with NLD often manifest emotional and relational difficulties that prevent them from adequately processing emotional information (Petti, Voelker, Shore, & Hayman-Abello, 2003; Rourke, 1995; see also Worling, Humphries, & Tannock, 1999). Finally, it has been found that children with NLD suffer from several impairments in social problem-solving, suggesting a reciprocal influence between socio-cognitive factors, the development and maintenance of pathological symptoms, and adaptation to the environment (Galway & Metsala, 2010). In summary, children with LD are an important population to be considered in the study of memory illusions. Several behavioral patterns could emerge from our research: one could expect a general poorer performance in recognition memory in these populations of children. Alternatively, memory performance, particularly memory illusions, may manifest differently within these unique groups of children with disabilities, depending on the purported mechanisms underlying the illusion. 2. The present study In the present study, children with NLD, children with dyslexia, and typically developing children were administered a false-memory task adapted from a paradigm previously used with typically developing children (Lyons, Ghetti, & Cornoldi, 2010) and children with ADHD (Mirandola et al., 2012). This particular paradigm allows emotional false memories to be investigated in both children and adults (Mirandola, Toffalini, Grassano, Cornoldi, & Melinder, 2013). Participants first study photographs that depict common actions for a variety of commonplace daily scenes. For each script, participants view typical scene-appropriate actions, as well as photographs that depict the effect of an action whose cause is not presented in the episode. Specifically, this paradigm allows for the investigation of two types of memory errors: gap-filling and causal errors incurred when one falsely recognizes, respectively, scripted information that was not presented (e.g., eating some food at dinner), or causal information (recognizing a cause photograph, i.e., ‘‘knocking over a bottle of water on the table’’ when they only viewed the effect of that cause, i.e., ‘‘pieces of a broken bottle on the floor’’).
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The two main objectives of the present research were: (1) to investigate whether children with learning disabilities are less prone to memory errors compared to typically developing children (as it has been observed with the DRM paradigm), specifically when scripted episodes that depict real-life events are presented at encoding, and (2) to evaluate whether differences in false memory formation could emerge as a function of developmental disability. Specifically, we expected that children with NLD would attend to the negatively charged events to a higher degree than their peers, due to their vulnerability to emotional distress, and would thus be more prone to evince false recognition for negatively charged episodes. This prediction is based on the foundation that memory errors are most likely to occur when the error is consistent with the semantic gist or theme of the studied material (Brainerd & Reyna, 2005; Howe, 2007), as in the case of script consistent non-presented lures (i.e., gap-filling error). When individuals erroneously attribute causes to experienced effects (i.e., inferential causal error), emotional involvement may be critical; stimuli with emotional valence have been argued to elicit gist connections more than stimuli of neutral valence (Brainerd, Stein, Silveira, Rohenkohl, & Reyna, 2008). Increased false recognition of negative actions is not expected in children with dyslexia; their overall reduced semantic elaboration abilities was expected to result in overall lower false recognition for causal inferences and gap-filling errors regardless of the valence of the stimuli. Finally, in the present study we wanted to test the subjective quality of the children’s memory experiences. We did so by asking children to generate Remember/Familiar judgments for each recognition decision, given initial evidence that children with developmental disabilities have different subjective memory experiences than their peers (Mirandola et al., 2011). Recollection and familiarity have been previously investigated in children with severe developmental disabilities (see Costanzo, Vicari, & Carlesimo, 2013 and Bigham, Boucher, Mayes, & Anns, 2010, for Williams’ syndrome and autism respectively), but it seems an important research avenue to explore in children with milder learning difficulties. It is possible that children with milder LD may display reduced subjective experience of recollection for both true and false recognition rates due to general impairment in semantic elaboration processes. This prediction is based on past findings in adolescents with reading comprehension difficulties that reported lower recollection rates than a control group, consistent with general memory impairments in children with learning disabilities (Mirandola et al., 2011). However, differences could emerge depending on the type of disability. Specifically, we predicted that children with NLD would display a higher tendency to experience subjective recollection for emotionally charged situations, given their often reported higher emotional involvement. Conversely, we expected a reduced subjective experience of recollection linked to both true and false memories in children with dyslexia, given their likely lower ability at handling conceptual information. 3. Method 3.1. Participants Fourteen children with NLD (F = 9; M = 5), 18 children with dyslexia (F = 11; M = 7), and 19 typically developing children (F = 9; M = 10) participated in this study (see Table 1 for mean participant age in months). The three groups did not differ in years of age: x2 (6, N = 51) = 2.81, p < .83. All children were Italian, and written consent was obtained from their parents before task administration. We ensured that the groups of children with NLD or dyslexia met specific diagnostic criteria, including a negative history of neurological or psychiatric impairments. Children were assessed for developmental disabilities by a team that included two licensed psychologists with a specific training in LD. Children were included in the NLD group if the following criteria were met: 1. good scores in the lexical decision task (50 percentile; Caldarola, Perini, & Cornoldi, 2012); 2. a very poor performance in the Memory of the Rey’s Complex Figure test (scores < 10 percentile; Osterrieth, 1944); 3. average performance in word and pseudo-word reading tasks (50 percentile in accuracy and speed; derived from Sartori, Job, & Tressoldi, 2007). Children were included in the dyslexia group if the following criteria were met:
Table 1 Means and standard deviations for age, cognitive abilities, socio-cultural status and the tests used for characterizing the three groups of children (typically developing children and children with nonverbal learning disability and dyslexia). Group
Age Cognitive abilities Socio-cultural status Lexical decision task Rey’s Complex Figure Word reading task (time) (z-score) Pseudo-word reading task (time) (z-score)
Typically developing
NLD
Dyslexia
M (SD)
M (SD)
M (SD)
153.8 (10.7) 2.89 (0.73) 1.58 (0.92) 50.16 (9.37) 21.31 (3.88) 0.10 (0.79) 0.58 (0.53)
151.4 (12.4) 3 (0.78) 1.5 (1.01) 47.36 (10.31) 15.89 (6.14) 0.11 (0.85) 0.03 (0.77)
152.1 (11.9) 2.72 (0.89) 1.5 (0.85) 27.72 (10.58) 19.83 (5.64) 1.82 (2.22) 1.48 (1.62)
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1. scores in the lexical decision task at least 1 SD below average; 2. scores 50 percentile in the Memory of the Rey’s Complex Figure test; 3. a low performance in both the word and the pseudo-word reading tasks (scores < 15 percentile in accuracy and at least 2 SD below average in reading speed). Typically developing children had average scores in all the above-mentioned tasks (Table 1). Children were matched for cognitive level and socio-cultural status, assessed through the SVS questionnaire (Cornoldi et al., 2003). The questionnaire includes items that ask teachers to estimate the child’s socio-cultural level (range 1–4; 1 = high socio-cultural level, 2 = medium-high; 3 = medium-low; 4 = very low) and general intellectual ability. Children scored as having low socio-cultural level and low intelligence were not recruited. Table 1 summarizes the descriptive statistics for the children’s performance by group (NLD, dyslexic and typically developing) and mean ages, cognitive abilities and socio-economic status. 3.2. Materials 3.2.1. Pictorial stimuli A series of color photographs representing 8 episodes, or scripts, was employed in this study. The episodes included: having a family dinner at home, playing at the playground, going shopping, waking up, doing homework after school, going on a bike trip, going to the doctor, and children performing a drama piece in a theater. For each episode, 14 photographs depicted actions that typically occur during the event (11 were used as target photographs in the encoding phase and 3 were used as distractors in the recognition phase), and 2 photographs depicted cause-effect scenes (the effect scene was studied whereas the cause scene was presented only during the recognition test). The emotionality of the effect photographs was balanced across scripts, such that the same cause could have two different outcomes: one negative and one neutral. For example, in the ‘‘going on a bike trip’’ event, the cause photograph that shows a child crossing the street without looking could be paired with either a photograph depicting an accident with a car, or a photograph depicting a car slowing down and letting the child cross. Finally, stimuli also included 10 photographs that were inconsistent with any of the 8 events, such as children playing on the beach, boys and girls at a party. 3.2.2. Recognition test A randomized sequence of 80 photographs was administered to all participants. For each of the 8 events, the recognition test included: (1) 4 old photographs, (2) 3 new photographs that were consistent with the event script (e.g., expected to elicit gap-filling errors), (3) 1 cause photograph whose effect had been presented during the encoding phase (i.e., expected to elicit causal inference errors). Finally, (4) 1 old photograph inconsistent with the script and (5) 1 new photograph inconsistent with the script were included. 3.3. Procedure 3.3.1. Encoding phase All children were tested individually in a quiet room at their school. They were informed that they would see a series of photographs depicting children engaged in various everyday actions and were instructed to pay close attention in order to understand what the series of actions portrayed. For each of the 8 episodes, participants viewed 12 photographs in a logical order; each slide appeared on the computer screen for 2 s, followed by a 2-s black slide. A slide that displayed the effect of an action, which could be either emotional or neutral, was included among these photographs for every series; the photograph corresponding to the cause was not presented during encoding. For each participant, 4 scripts included emotional outcomes and 4 scripts neutral outcomes. The emotionality of the outcomes was counterbalanced among participants. Further, 5 photographs inconsistent with any of the presented episodes were shown at the beginning of the slide show, and 5 at the end of the presentation. The overall duration of the encoding phase was approximately 7 min. After a 15-min retention interval, the recognition test was administered. During the interval, children were required to perform the Rey’s Complex Figure, as well as word and non-word reading tasks in order to better assess their abilities, which helped us more accurately characterize the three groups of participants. 3.3.2. Recognition phase The recognition memory test consisted of a self-paced yes/no recognition test: for each photograph participants responded ‘‘yes’’ when they thought they had seen the photograph during encoding, and ‘‘no’’ when they thought they had not seen the photograph before. Further, for each recognized photograph, participants categorized the photograph as ‘‘Remembered’’ or ‘‘Familiar’’. Participants were instructed to select Remember when they had a clear memory of seeing the photograph and further, could retrieve such qualitative features as contextual details or thoughts that came to mind during viewing; they were instead instructed to select Familiar, when they had the feeling they had seen the photograph before, but could not retrieve any detail or thought related to its encounter. We adapted the instructions from those developed for child samples in previous research (see Ghetti, Mirandola, Angelini, Cornoldi, & Ciaramelli, 2011).
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4. Results Preliminary analysis showed that there were no differences based on gender (p > .05), this variable was thus excluded from subsequent analyses. 4.1. True recognition A 3 (group: control vs. NLD vs. dyslexia) 2 (item type: consistent vs. inconsistent) mixed ANOVA, with ‘‘yes’’ responses to target stimuli did not reveal any main or interactive effect (F > 1, p > .05). The proportions of true recognition presented only slight and non-significant differences between the three groups. The rates of hits-consistent (i.e., true recognitions of the target photographs consistent with the script) were the following: M = .78 (SD = .12), M = .75 (SD = .13), and M = .72 (SD = .18) respectively for the typically developing children, children with NLD, and children with dyslexia. The rates of hitsinconsistent (i.e., true recognitions of the target photographs inconsistent with any of the scripts) were the following: M = .76 (SD = .24), M = .72 (SD = .19), and M = .76 (SD = .18) respectively for the typically developing children, children with NLD and children with dyslexia. We also computed a measure of sensitivity to see whether differences between groups would emerge. We obtained d0 scores collapsing both types of errors and emotional context. When we entered the d0 scores in a between-participants ANOVA, we did not find a significant difference between groups, confirming that all three groups were similarly able to discriminate target from distractor photographs. Means of the d0 scores were: typically developing children, M = 1.49 (SD = .87); children with NLD, M = 1.41 (SD = .74); children with dyslexia, M = 1.39 (SD = .97). 4.2. False recognition The subsequent analysis concerned the main goals of the present study and examined whether, despite a similar proportion of hits, the three groups differed in memory errors. In order to evaluate whether there were differences on the propensity to endorse false memories, a 3 (group: control vs. NLD vs. dyslexia) 2 (type of error: gap-filling vs. causal) 2 (emotional content: negative vs. neutral) mixed ANOVA on the proportion of ‘‘yes’’ responses to distractor stimuli was performed. This analysis revealed a main effect of error type, F(1,48) = 50.35, p < .001, h2p ¼ :51. This effect was qualified by an interaction between group and error type, F(2,48) = 6.54, p < .01, h2p ¼ :21. Post-hoc comparisons (with Bonferroni correction) showed that the control group and the NLD group produced a significantly higher proportion of causal errors compared to gap-filling errors (see Table 2), whereas in the group of children with dyslexia the causal errors were relatively low and did not significantly differ from the gap-filling errors. Further, a crucial 3-way interaction between group, type of error and emotional context emerged, F(2,48) = 3.97, p < .05, h2p ¼ :14. Post-hoc tests showed that the NLD group experienced more causal errors with negative content compared to both the group of children with dyslexia and the control group (p < .05) and, furthermore, children in the NLD group produced a higher proportion of emotional causal error compared to neutral causal errors (p < .05). In the other two participant groups, the opposite trend was evident (see Table 2 and Fig. 1). From a qualitative perspective, concerning the specific case of the group of children with dyslexia, it must be noted that 7 children included in this group had higher scores in the lexical decision task, which implies higher semantic processing ability. These 7 children were more likely to produce, overall, memory errors (mean proportion of total errors, i.e., combining gap-filling and causal errors = .30) than children with low scores obtained in the lexical decision task (mean proportion = .24). This finding suggests that semantic processing ability may be an indicator of the propensity to endorse false recognition and that the group of children with dyslexia, in the present study, was not overall characterized by a very low level of semantic abilities.
Table 2 Mean proportions (and standard deviations) of gap-filling and causal errors (and associated Remember and Familiar responses) as a function of emotional content in the three groups of participants. Gap-filling errors
Causal errors
Emotional context
Neutral context
Emotional outcome
Neutral outcome
Typically developing Memory errors Remember Familiar
.25 (.23) .14 (.21) .11 (.12)
.25 (.20) .11 (.14) .14 (.16)
.34 (.27) .19 (.22) .14 (.17)
.43 (.26) .22 (.16) .21 (.25)
NLD Memory errors Remember Familiar
.18 (.12) .08 (.09) .10 (.11)
.22 (.19) .09 (.14) .12 (.13)
.59 (.33) .39 (.28) .20 (.28)
.37 (.27) .28 (.23) .09 (.15)
Dyslexia Memory errors Remember Familiar
.24 (.24) .14 (.20) .10 (.11)
.25 (.20) .16 (.18) .09 (.12)
.29 (.20) .22 (.20) .07 (.14)
.35 (.24) .29 (.23) .06 (.10)
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1 0.9 0.8 0.7 0.6 0.5
NLD
0.4
Dyslexia
0.3
TD
0.2 0.1 0 Emoonal
Neutral
Gap-filling errors
Emoonal
Neutral
Causal errors
Fig. 1. Mean proportions of memory errors in the three groups of participants.
Finally, we examined Remember and Familiar responses focusing on the subjective experiences of memory errors (see Table 2). A 3 (group) 2 (type of error) 2 (emotional content) mixed ANOVA conducted on the Remember judgments associated with ‘‘yes’’ responses to distractor stimuli, revealed a significant main effect of error type, F(1,48) = 39.40, p < .001, h2p ¼ :45, such that, across groups, more Remember responses were associated with causal errors compared to gap-filling errors. Further, a significant interaction between error type and group was found, F(2,48) = 4.65, p < .05, h2p ¼ :16; post-hoc analyses showed that the NLD group associated a higher proportion of Remember responses to causal errors (regardless of emotional context) compared to the control group and children with dyslexia (p < .05). The same analysis conducted on the Familiar responses associated with memory errors did not reveal any significant main effect or interaction; however, there was a tendency toward a group by error type interaction (F(2,48) = 2.89, p = .065) showing that typically developing children were more likely to select the Familiar option when a contextually neutral causal error occurred, compared to the other two groups. 5. Discussion The present study was aimed at characterizing the false memory profiles of two types of learning disabilities, namely NLD and dyslexia. Learning disabilities are associated with a number of poor learning outcomes, including memory problems (Hulme & Snowling, 2009). For this reason we thought it was important to establish whether children with specific learning disabilities would present memory difficulties for daily events. Moreover, we were interested in investigating whether these children would also produce fewer errors reflecting causal inferences or gap-filling processes, compared to typically developing children. Finally, we sought to differentiate the pattern of memory performance depending on the nature of the disability. To achieve these goals, we focused on two types of LD, i.e. NLD and dyslexia. The former is primarily characterized by visuospatial and visuoconstructive difficulties and, most importantly for the specific purposes of the present study, by difficulty dealing with emotional material (Rourke, 1995). Dyslexia is characterized by poor reading abilities, stemming from phonological, orthographic, and semantic deficits (Hulme & Snowling, 2009). Given these different profiles, we expected that the two groups would exhibit distinct patterns of memory deficits. Specifically, we expected that children with NLD would exhibit more errors when exposed to emotionally charged events and children with dyslexia would exhibit an overall reduction in memory errors compared to a control group. While we did not find an overall reduced false recognition rate in children with learning disabilities compared to typically developing children, we did find differences in false recognition rates dependent on the nature of the learning disability. Whereas children with NLD endorsed more causal errors than gap-filling errors (and to a lesser but still significant extent this was also the case for typically developing children), this pattern of results was not evident in children with dyslexia; indeed, this latter group produced similar rates of both types of error (as indicated by a lower propensity to accept the inferred cause of the viewed effect). The reduced tendency to commit causal errors, which are thought to be linked to recollection and are more likely to result from conceptual processing of the studied materials (Lyons et al., 2010), suggests reduced semantic processing ability in children with dyslexia. This is conceptually similar to the results obtained with a different paradigm in adolescents experiencing text comprehension difficulties (Mirandola et al., 2011). Including children in the dyslexic group with high lexical skills might in part explain why a significantly lower number of memory errors, when compared to the control group, failed to emerge.
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In contrast, children with NLD were more likely to make causal errors when exposed to negatively valenced episodes than both typically developing children and children with dyslexia. Further, within the NLD group, more emotional causal distractors were falsely recognized than neutral ones, suggesting a facilitating role of emotions in the production of this particular type of inferential error. Children with NLD have been described as having difficulties understanding emotions and dealing with them, and as having depressive symptoms (Bender, Rosenkrans, & Crane, 1999). The unseen causes of negatively charged events may stem more automatically in these children, and thus may be easily erroneously inferred. This is further supported by subjective reports given by children with NLD: indeed, they not only failed to reject not-seen causes of emotional events, but they also claimed to vividly remember them. Our above findings may be supported by both fuzzy-trace theory’s and associative-activation theory’s predictions. According to the former approach (Brainerd, Reyna, et al., 2008; Brainerd, Stein, et al., 2008), emotionally valenced stimuli favor gist connections more than neutrally valenced ones. Moreover, gist connections are responsible for false memory formation, thus, it follows that an enhanced emotional impact of studied items should boost memory errors. It could be argued that children with NLD, as more emotionally involved in events than the other groups, had a higher tendency to establish gist connections for emotional events. According to the associative-activation theory (Howe, 2005, 2008), the nonpresented items that are semantically connected with studied items are activated, at encoding, to a higher extent than non-semantically related ones. When emotionally charged items are activated in memory, there is an enhanced probability that related negatively charged information will be incorporated in false recollection (Howe et al., 2010); this seems particularly true for recognition tasks and may thus explain our findings of enhanced false recognition rates for causal errors in the group of NLD children. We note that our finding is specific for inferential causal errors and not for gap-filling errors. Indeed, non-presented causal scenes were tightly bound to the emotional content of the experienced effect, whereas non encountered script-consistent information was only indirectly influenced by the emotionality of the action effects. Children with NLD have been found to manifest more depressive symptoms than other learning disabilities (Bender et al., 1999; Spreen, 2011), thus the current data may be explained also taking into account the ‘‘mood-congruent effect’’ perspective. The available research on the effect of clinical depression on false memories points out that individuals with depressive symptoms tend to incorporate more negatively valenced non-experienced events into their memories than neutral ones (e.g., Howe & Malone, 2011). In the current study we only included negative events and therefore we cannot exclude that the pattern of errors of children with NLD would be different with emotionally charged, but positive events. It must be noted that for a number of reasons, including the ability to use an already validated paradigm, and avoiding possible confusion due to the combination of different types of emotional events, in the present study we only examined the emotionally negative effects (contrasted with neutral events). This allows our research to inform real world applications, such as the eyewitness context. Children who are asked to provide allegations in the courtroom are primarily prompted to recall negative events. Nevertheless, future research should also investigate whether children with NLD are more vulnerable to emotional events overall (including positive ones), or whether their proneness to memory illusions is specific to negative situations. In conclusion, our study offers important insights on memory for everyday actions in children with learning disabilities. In particular, the present findings showed that recognition memory can equal that of typically developing children, but their false recognition differs. This can be useful for understanding both the characteristics of memory distortions and the abilities of children with LD. Indeed, our results offer important implications both for educational and forensic contexts, as they show that different groups of LD may produce different patterns of memory errors. Even though further investigations with larger samples and different memory paradigms are needed, children with NLD have been found to be particularly vulnerable to emotional content and thus biased in attributing negative effects to unseen causes. Acknowledgment We thank Julia Ross for editorial assistance in the preparation of this manuscript.
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Contents lists available at ScienceDirect
Research in Developmental Disabilities
Emotional false memories in children with learning disabilities Chiara Mirandola a,*, Nunzia Losito a, Simona Ghetti b, Cesare Cornoldi a a b
Department of General Psychology, University of Padova, Italy Department of Psychology and Center for Mind and Brain, University of California, Davis, United States
A R T I C L E I N F O
A B S T R A C T
Article history: Received 25 August 2013 Received in revised form 5 November 2013 Accepted 6 November 2013 Available online 30 November 2013
Research has shown that children with learning disabilities (LD) are less prone to evince associative illusions of memory as a result of impairments in their ability to engage in semantic processing. However, it is unclear whether this observation is true for scripted life events, especially if they include emotional content, or across a broad spectrum of learning disabilities. The present study addressed these issues by assessing recognition memory for script-like information in children with nonverbal learning disability (NLD), children with dyslexia, and typically developing children (N = 51). Participants viewed photographs about 8 common events (e.g., family dinner), and embedded in each episode was either a negative or a neutral consequence of an unseen action. Children’s memory was then tested on a yes/no recognition task that included old and new photographs. Results showed that the three groups performed similarly in recognizing target photographs, but exhibited differences in memory errors. Compared to other groups, children with NLD were more likely to falsely recognize photographs that depicted an unseen cause of an emotional seen event and associated more ‘‘Remember’’ responses to these errors. Children with dyslexia were equally likely to falsely recognize both unseen causes of seen photographs and photographs generally consistent with the script, whereas the other participant groups were more likely to falsely recognize unseen causes rather than script-consistent distractors. Results are interpreted in terms of mechanisms underlying false memories’ formation in different clinical populations of children with LD. ß 2013 Elsevier Ltd. All rights reserved.
Keywords: Specific learning disabilities False memories Emotional content
1. Introduction Memory illusions occur quite frequently in the laboratory as well as in real life, and their developmental trajectory depends on the nature of the illusion. When memory illusions stem from processing semantically related information (e.g., Deese–Roediger–McDermott (DRM) paradigm: Brainerd, Holliday, & Reyna, 2004; connected–meaning paradigms: Howe, 2006), typically developing children often demonstrate age-related increases in the frequency of memory errors (Brainerd, Reyna, & Ceci, 2008; Brainerd, Reyna, & Zember, 2011; but see Ghetti, Qin, & Goodman, 2002; Lampinen, Leding, Reed, & Odegard, 2006). The DRM paradigm involves the presentation of several lists of semantically related words (e.g., sick, nurse, medicine). Within each list, all words are associated to a single word not presented during encoding, the critical lure (in this
* Corresponding author at: Department of General Psychology, University of Padova, Via Venezia 8, 35131 Padova, Italy. Tel.: +39 049 827 6617; fax: +39 049 827 6600. E-mail address: [email protected] (C. Mirandola). 0891-4222/$ – see front matter ß 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.ridd.2013.11.004
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example, doctor). At retrieval, adults and older children falsely recognize the critical lures almost at the same rate as target words. Younger children recognize the critical lures to a lesser extent than older children and adults, thus committing fewer memory errors. This developmental trend persists even when emotionally charged stimuli are used instead of neutral stimuli (Brainerd, Holliday, Reyna, Yang, & Toglia, 2010; Howe, 2007; Howe, Candel, Otgaar, Malone, & Wimmer, 2010, Experiment 2). However, it is unclear to what extent these observed trends may apply to memory for life events, as well as to special clinical populations. Most of the available research on false memory formation in certain clinical populations of children primarily focuses on the implication of eyewitness memory or suggestibility in maltreated children (Howe, Cicchetti, Toth, & Cerrito, 2004), children within autism spectrum disorders (McCrory, Henry, & Happe`, 2007), or other severe developmental disabilities, such as intellectual disabilities (Brown, Lewis, Lamb, & Stephens, 2012; Henry & Gudjonsson, 1999, 2004; Young, Powell, & Dudgeon, 2003). The majority of these studies are aimed at evaluating the best way to administer a cognitive interview when children are either victims or witnesses of abuse and are required to provide allegations in the courtroom. However, little is known about the functioning of basic underlying memory processes in these populations. Furthermore, only a few studies have investigated memory accuracy and memory distortions in special populations of children with academic difficulties, such as children with reading comprehension difficulty (Mirandola, Del Prete, Ghetti, & Cornoldi, 2011; Weekes, Hamilton, Oakhill, & Holliday, 2008), children with attention deficit/hyperactivity disorder (ADHD; Mirandola, Paparella, Re, Ghetti, & Cornoldi, 2012), and children with general learning disabilities (Brainerd, Forrest, Karibian, & Reyna, 2006). Research conducted with the DRM paradigm (Roediger & McDermott, 1995) has shown that children with learning disabilities produce fewer memory errors than typically developing children (Brainerd et al., 2006; Weekes et al., 2008). This result has been associated with lower semantic processing abilities that prevent children with disabilities from relying on the gist of the wordlists, thus mimicking the pattern of errors found when comparing younger to older children. It must be noted that these studies focused specifically on memory errors, and it is unclear whether semantic processing difficulties associated with learning disabilities may influence the way in which children retain correct information as well. A paradigm specifically designed to investigate recognition memory and text-based detail recollection in adolescents with poor semantic text processing ability revealed an overall impaired recognition of sentences and related recollection (i.e., lower proportion of Remember judgments in association with correctly recognized target sentences) in these students, compared to a control group, despite both groups displaying similar recognition memory for isolated words (Mirandola et al., 2011). The present study was designed to investigate memory accuracy and errors in two distinct groups of children with learning disabilities, namely children with nonverbal learning disability (NLD) and children with dyslexia. Children with dyslexia are characterized by poor reading decoding abilities and sometimes show reduced semantic processing abilities (Betjemann & Keenan, 2008), as confirmed by recent studies combining fMRI and ERPs (Schulz et al., 2008, 2009). Whereas children with dyslexia present both language and reading skills impairments, children with NLD have good verbal skills, but a neuropsychological profile characterized by impairments in nonverbal abilities (Rourke, 1995). One of the identifying features of NLD is a significantly higher performance on tasks measuring verbal intelligence than on those measuring visuospatial intelligence (Cornoldi, Venneri, Marconato, Molin, & Montinari, 2003; Johnson, 1987; Mammarella et al., 2009; Weintraub & Mesulam, 1983). A factor underlying this discrepancy is that children with NLD possess poor visuospatial and visuoconstructive abilities, which would explain their difficulties in a broad range of school and everyday life activities including, but not limited to, mathematics, drawing, and spatial orientation (Cornoldi, Dalla Vecchia, & Tressoldi, 1995; Cornoldi, Rigoni, Tressoldi, & Vio, 1999; Cornoldi & Vecchi, 2003; Mammarella & Cornoldi, 2005). Most important for the current purposes, children with NLD often manifest emotional and relational difficulties that prevent them from adequately processing emotional information (Petti, Voelker, Shore, & Hayman-Abello, 2003; Rourke, 1995; see also Worling, Humphries, & Tannock, 1999). Finally, it has been found that children with NLD suffer from several impairments in social problem-solving, suggesting a reciprocal influence between socio-cognitive factors, the development and maintenance of pathological symptoms, and adaptation to the environment (Galway & Metsala, 2010). In summary, children with LD are an important population to be considered in the study of memory illusions. Several behavioral patterns could emerge from our research: one could expect a general poorer performance in recognition memory in these populations of children. Alternatively, memory performance, particularly memory illusions, may manifest differently within these unique groups of children with disabilities, depending on the purported mechanisms underlying the illusion. 2. The present study In the present study, children with NLD, children with dyslexia, and typically developing children were administered a false-memory task adapted from a paradigm previously used with typically developing children (Lyons, Ghetti, & Cornoldi, 2010) and children with ADHD (Mirandola et al., 2012). This particular paradigm allows emotional false memories to be investigated in both children and adults (Mirandola, Toffalini, Grassano, Cornoldi, & Melinder, 2013). Participants first study photographs that depict common actions for a variety of commonplace daily scenes. For each script, participants view typical scene-appropriate actions, as well as photographs that depict the effect of an action whose cause is not presented in the episode. Specifically, this paradigm allows for the investigation of two types of memory errors: gap-filling and causal errors incurred when one falsely recognizes, respectively, scripted information that was not presented (e.g., eating some food at dinner), or causal information (recognizing a cause photograph, i.e., ‘‘knocking over a bottle of water on the table’’ when they only viewed the effect of that cause, i.e., ‘‘pieces of a broken bottle on the floor’’).
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The two main objectives of the present research were: (1) to investigate whether children with learning disabilities are less prone to memory errors compared to typically developing children (as it has been observed with the DRM paradigm), specifically when scripted episodes that depict real-life events are presented at encoding, and (2) to evaluate whether differences in false memory formation could emerge as a function of developmental disability. Specifically, we expected that children with NLD would attend to the negatively charged events to a higher degree than their peers, due to their vulnerability to emotional distress, and would thus be more prone to evince false recognition for negatively charged episodes. This prediction is based on the foundation that memory errors are most likely to occur when the error is consistent with the semantic gist or theme of the studied material (Brainerd & Reyna, 2005; Howe, 2007), as in the case of script consistent non-presented lures (i.e., gap-filling error). When individuals erroneously attribute causes to experienced effects (i.e., inferential causal error), emotional involvement may be critical; stimuli with emotional valence have been argued to elicit gist connections more than stimuli of neutral valence (Brainerd, Stein, Silveira, Rohenkohl, & Reyna, 2008). Increased false recognition of negative actions is not expected in children with dyslexia; their overall reduced semantic elaboration abilities was expected to result in overall lower false recognition for causal inferences and gap-filling errors regardless of the valence of the stimuli. Finally, in the present study we wanted to test the subjective quality of the children’s memory experiences. We did so by asking children to generate Remember/Familiar judgments for each recognition decision, given initial evidence that children with developmental disabilities have different subjective memory experiences than their peers (Mirandola et al., 2011). Recollection and familiarity have been previously investigated in children with severe developmental disabilities (see Costanzo, Vicari, & Carlesimo, 2013 and Bigham, Boucher, Mayes, & Anns, 2010, for Williams’ syndrome and autism respectively), but it seems an important research avenue to explore in children with milder learning difficulties. It is possible that children with milder LD may display reduced subjective experience of recollection for both true and false recognition rates due to general impairment in semantic elaboration processes. This prediction is based on past findings in adolescents with reading comprehension difficulties that reported lower recollection rates than a control group, consistent with general memory impairments in children with learning disabilities (Mirandola et al., 2011). However, differences could emerge depending on the type of disability. Specifically, we predicted that children with NLD would display a higher tendency to experience subjective recollection for emotionally charged situations, given their often reported higher emotional involvement. Conversely, we expected a reduced subjective experience of recollection linked to both true and false memories in children with dyslexia, given their likely lower ability at handling conceptual information. 3. Method 3.1. Participants Fourteen children with NLD (F = 9; M = 5), 18 children with dyslexia (F = 11; M = 7), and 19 typically developing children (F = 9; M = 10) participated in this study (see Table 1 for mean participant age in months). The three groups did not differ in years of age: x2 (6, N = 51) = 2.81, p < .83. All children were Italian, and written consent was obtained from their parents before task administration. We ensured that the groups of children with NLD or dyslexia met specific diagnostic criteria, including a negative history of neurological or psychiatric impairments. Children were assessed for developmental disabilities by a team that included two licensed psychologists with a specific training in LD. Children were included in the NLD group if the following criteria were met: 1. good scores in the lexical decision task (50 percentile; Caldarola, Perini, & Cornoldi, 2012); 2. a very poor performance in the Memory of the Rey’s Complex Figure test (scores < 10 percentile; Osterrieth, 1944); 3. average performance in word and pseudo-word reading tasks (50 percentile in accuracy and speed; derived from Sartori, Job, & Tressoldi, 2007). Children were included in the dyslexia group if the following criteria were met:
Table 1 Means and standard deviations for age, cognitive abilities, socio-cultural status and the tests used for characterizing the three groups of children (typically developing children and children with nonverbal learning disability and dyslexia). Group
Age Cognitive abilities Socio-cultural status Lexical decision task Rey’s Complex Figure Word reading task (time) (z-score) Pseudo-word reading task (time) (z-score)
Typically developing
NLD
Dyslexia
M (SD)
M (SD)
M (SD)
153.8 (10.7) 2.89 (0.73) 1.58 (0.92) 50.16 (9.37) 21.31 (3.88) 0.10 (0.79) 0.58 (0.53)
151.4 (12.4) 3 (0.78) 1.5 (1.01) 47.36 (10.31) 15.89 (6.14) 0.11 (0.85) 0.03 (0.77)
152.1 (11.9) 2.72 (0.89) 1.5 (0.85) 27.72 (10.58) 19.83 (5.64) 1.82 (2.22) 1.48 (1.62)
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1. scores in the lexical decision task at least 1 SD below average; 2. scores 50 percentile in the Memory of the Rey’s Complex Figure test; 3. a low performance in both the word and the pseudo-word reading tasks (scores < 15 percentile in accuracy and at least 2 SD below average in reading speed). Typically developing children had average scores in all the above-mentioned tasks (Table 1). Children were matched for cognitive level and socio-cultural status, assessed through the SVS questionnaire (Cornoldi et al., 2003). The questionnaire includes items that ask teachers to estimate the child’s socio-cultural level (range 1–4; 1 = high socio-cultural level, 2 = medium-high; 3 = medium-low; 4 = very low) and general intellectual ability. Children scored as having low socio-cultural level and low intelligence were not recruited. Table 1 summarizes the descriptive statistics for the children’s performance by group (NLD, dyslexic and typically developing) and mean ages, cognitive abilities and socio-economic status. 3.2. Materials 3.2.1. Pictorial stimuli A series of color photographs representing 8 episodes, or scripts, was employed in this study. The episodes included: having a family dinner at home, playing at the playground, going shopping, waking up, doing homework after school, going on a bike trip, going to the doctor, and children performing a drama piece in a theater. For each episode, 14 photographs depicted actions that typically occur during the event (11 were used as target photographs in the encoding phase and 3 were used as distractors in the recognition phase), and 2 photographs depicted cause-effect scenes (the effect scene was studied whereas the cause scene was presented only during the recognition test). The emotionality of the effect photographs was balanced across scripts, such that the same cause could have two different outcomes: one negative and one neutral. For example, in the ‘‘going on a bike trip’’ event, the cause photograph that shows a child crossing the street without looking could be paired with either a photograph depicting an accident with a car, or a photograph depicting a car slowing down and letting the child cross. Finally, stimuli also included 10 photographs that were inconsistent with any of the 8 events, such as children playing on the beach, boys and girls at a party. 3.2.2. Recognition test A randomized sequence of 80 photographs was administered to all participants. For each of the 8 events, the recognition test included: (1) 4 old photographs, (2) 3 new photographs that were consistent with the event script (e.g., expected to elicit gap-filling errors), (3) 1 cause photograph whose effect had been presented during the encoding phase (i.e., expected to elicit causal inference errors). Finally, (4) 1 old photograph inconsistent with the script and (5) 1 new photograph inconsistent with the script were included. 3.3. Procedure 3.3.1. Encoding phase All children were tested individually in a quiet room at their school. They were informed that they would see a series of photographs depicting children engaged in various everyday actions and were instructed to pay close attention in order to understand what the series of actions portrayed. For each of the 8 episodes, participants viewed 12 photographs in a logical order; each slide appeared on the computer screen for 2 s, followed by a 2-s black slide. A slide that displayed the effect of an action, which could be either emotional or neutral, was included among these photographs for every series; the photograph corresponding to the cause was not presented during encoding. For each participant, 4 scripts included emotional outcomes and 4 scripts neutral outcomes. The emotionality of the outcomes was counterbalanced among participants. Further, 5 photographs inconsistent with any of the presented episodes were shown at the beginning of the slide show, and 5 at the end of the presentation. The overall duration of the encoding phase was approximately 7 min. After a 15-min retention interval, the recognition test was administered. During the interval, children were required to perform the Rey’s Complex Figure, as well as word and non-word reading tasks in order to better assess their abilities, which helped us more accurately characterize the three groups of participants. 3.3.2. Recognition phase The recognition memory test consisted of a self-paced yes/no recognition test: for each photograph participants responded ‘‘yes’’ when they thought they had seen the photograph during encoding, and ‘‘no’’ when they thought they had not seen the photograph before. Further, for each recognized photograph, participants categorized the photograph as ‘‘Remembered’’ or ‘‘Familiar’’. Participants were instructed to select Remember when they had a clear memory of seeing the photograph and further, could retrieve such qualitative features as contextual details or thoughts that came to mind during viewing; they were instead instructed to select Familiar, when they had the feeling they had seen the photograph before, but could not retrieve any detail or thought related to its encounter. We adapted the instructions from those developed for child samples in previous research (see Ghetti, Mirandola, Angelini, Cornoldi, & Ciaramelli, 2011).
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4. Results Preliminary analysis showed that there were no differences based on gender (p > .05), this variable was thus excluded from subsequent analyses. 4.1. True recognition A 3 (group: control vs. NLD vs. dyslexia) 2 (item type: consistent vs. inconsistent) mixed ANOVA, with ‘‘yes’’ responses to target stimuli did not reveal any main or interactive effect (F > 1, p > .05). The proportions of true recognition presented only slight and non-significant differences between the three groups. The rates of hits-consistent (i.e., true recognitions of the target photographs consistent with the script) were the following: M = .78 (SD = .12), M = .75 (SD = .13), and M = .72 (SD = .18) respectively for the typically developing children, children with NLD, and children with dyslexia. The rates of hitsinconsistent (i.e., true recognitions of the target photographs inconsistent with any of the scripts) were the following: M = .76 (SD = .24), M = .72 (SD = .19), and M = .76 (SD = .18) respectively for the typically developing children, children with NLD and children with dyslexia. We also computed a measure of sensitivity to see whether differences between groups would emerge. We obtained d0 scores collapsing both types of errors and emotional context. When we entered the d0 scores in a between-participants ANOVA, we did not find a significant difference between groups, confirming that all three groups were similarly able to discriminate target from distractor photographs. Means of the d0 scores were: typically developing children, M = 1.49 (SD = .87); children with NLD, M = 1.41 (SD = .74); children with dyslexia, M = 1.39 (SD = .97). 4.2. False recognition The subsequent analysis concerned the main goals of the present study and examined whether, despite a similar proportion of hits, the three groups differed in memory errors. In order to evaluate whether there were differences on the propensity to endorse false memories, a 3 (group: control vs. NLD vs. dyslexia) 2 (type of error: gap-filling vs. causal) 2 (emotional content: negative vs. neutral) mixed ANOVA on the proportion of ‘‘yes’’ responses to distractor stimuli was performed. This analysis revealed a main effect of error type, F(1,48) = 50.35, p < .001, h2p ¼ :51. This effect was qualified by an interaction between group and error type, F(2,48) = 6.54, p < .01, h2p ¼ :21. Post-hoc comparisons (with Bonferroni correction) showed that the control group and the NLD group produced a significantly higher proportion of causal errors compared to gap-filling errors (see Table 2), whereas in the group of children with dyslexia the causal errors were relatively low and did not significantly differ from the gap-filling errors. Further, a crucial 3-way interaction between group, type of error and emotional context emerged, F(2,48) = 3.97, p < .05, h2p ¼ :14. Post-hoc tests showed that the NLD group experienced more causal errors with negative content compared to both the group of children with dyslexia and the control group (p < .05) and, furthermore, children in the NLD group produced a higher proportion of emotional causal error compared to neutral causal errors (p < .05). In the other two participant groups, the opposite trend was evident (see Table 2 and Fig. 1). From a qualitative perspective, concerning the specific case of the group of children with dyslexia, it must be noted that 7 children included in this group had higher scores in the lexical decision task, which implies higher semantic processing ability. These 7 children were more likely to produce, overall, memory errors (mean proportion of total errors, i.e., combining gap-filling and causal errors = .30) than children with low scores obtained in the lexical decision task (mean proportion = .24). This finding suggests that semantic processing ability may be an indicator of the propensity to endorse false recognition and that the group of children with dyslexia, in the present study, was not overall characterized by a very low level of semantic abilities.
Table 2 Mean proportions (and standard deviations) of gap-filling and causal errors (and associated Remember and Familiar responses) as a function of emotional content in the three groups of participants. Gap-filling errors
Causal errors
Emotional context
Neutral context
Emotional outcome
Neutral outcome
Typically developing Memory errors Remember Familiar
.25 (.23) .14 (.21) .11 (.12)
.25 (.20) .11 (.14) .14 (.16)
.34 (.27) .19 (.22) .14 (.17)
.43 (.26) .22 (.16) .21 (.25)
NLD Memory errors Remember Familiar
.18 (.12) .08 (.09) .10 (.11)
.22 (.19) .09 (.14) .12 (.13)
.59 (.33) .39 (.28) .20 (.28)
.37 (.27) .28 (.23) .09 (.15)
Dyslexia Memory errors Remember Familiar
.24 (.24) .14 (.20) .10 (.11)
.25 (.20) .16 (.18) .09 (.12)
.29 (.20) .22 (.20) .07 (.14)
.35 (.24) .29 (.23) .06 (.10)
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1 0.9 0.8 0.7 0.6 0.5
NLD
0.4
Dyslexia
0.3
TD
0.2 0.1 0 Emoonal
Neutral
Gap-filling errors
Emoonal
Neutral
Causal errors
Fig. 1. Mean proportions of memory errors in the three groups of participants.
Finally, we examined Remember and Familiar responses focusing on the subjective experiences of memory errors (see Table 2). A 3 (group) 2 (type of error) 2 (emotional content) mixed ANOVA conducted on the Remember judgments associated with ‘‘yes’’ responses to distractor stimuli, revealed a significant main effect of error type, F(1,48) = 39.40, p < .001, h2p ¼ :45, such that, across groups, more Remember responses were associated with causal errors compared to gap-filling errors. Further, a significant interaction between error type and group was found, F(2,48) = 4.65, p < .05, h2p ¼ :16; post-hoc analyses showed that the NLD group associated a higher proportion of Remember responses to causal errors (regardless of emotional context) compared to the control group and children with dyslexia (p < .05). The same analysis conducted on the Familiar responses associated with memory errors did not reveal any significant main effect or interaction; however, there was a tendency toward a group by error type interaction (F(2,48) = 2.89, p = .065) showing that typically developing children were more likely to select the Familiar option when a contextually neutral causal error occurred, compared to the other two groups. 5. Discussion The present study was aimed at characterizing the false memory profiles of two types of learning disabilities, namely NLD and dyslexia. Learning disabilities are associated with a number of poor learning outcomes, including memory problems (Hulme & Snowling, 2009). For this reason we thought it was important to establish whether children with specific learning disabilities would present memory difficulties for daily events. Moreover, we were interested in investigating whether these children would also produce fewer errors reflecting causal inferences or gap-filling processes, compared to typically developing children. Finally, we sought to differentiate the pattern of memory performance depending on the nature of the disability. To achieve these goals, we focused on two types of LD, i.e. NLD and dyslexia. The former is primarily characterized by visuospatial and visuoconstructive difficulties and, most importantly for the specific purposes of the present study, by difficulty dealing with emotional material (Rourke, 1995). Dyslexia is characterized by poor reading abilities, stemming from phonological, orthographic, and semantic deficits (Hulme & Snowling, 2009). Given these different profiles, we expected that the two groups would exhibit distinct patterns of memory deficits. Specifically, we expected that children with NLD would exhibit more errors when exposed to emotionally charged events and children with dyslexia would exhibit an overall reduction in memory errors compared to a control group. While we did not find an overall reduced false recognition rate in children with learning disabilities compared to typically developing children, we did find differences in false recognition rates dependent on the nature of the learning disability. Whereas children with NLD endorsed more causal errors than gap-filling errors (and to a lesser but still significant extent this was also the case for typically developing children), this pattern of results was not evident in children with dyslexia; indeed, this latter group produced similar rates of both types of error (as indicated by a lower propensity to accept the inferred cause of the viewed effect). The reduced tendency to commit causal errors, which are thought to be linked to recollection and are more likely to result from conceptual processing of the studied materials (Lyons et al., 2010), suggests reduced semantic processing ability in children with dyslexia. This is conceptually similar to the results obtained with a different paradigm in adolescents experiencing text comprehension difficulties (Mirandola et al., 2011). Including children in the dyslexic group with high lexical skills might in part explain why a significantly lower number of memory errors, when compared to the control group, failed to emerge.
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In contrast, children with NLD were more likely to make causal errors when exposed to negatively valenced episodes than both typically developing children and children with dyslexia. Further, within the NLD group, more emotional causal distractors were falsely recognized than neutral ones, suggesting a facilitating role of emotions in the production of this particular type of inferential error. Children with NLD have been described as having difficulties understanding emotions and dealing with them, and as having depressive symptoms (Bender, Rosenkrans, & Crane, 1999). The unseen causes of negatively charged events may stem more automatically in these children, and thus may be easily erroneously inferred. This is further supported by subjective reports given by children with NLD: indeed, they not only failed to reject not-seen causes of emotional events, but they also claimed to vividly remember them. Our above findings may be supported by both fuzzy-trace theory’s and associative-activation theory’s predictions. According to the former approach (Brainerd, Reyna, et al., 2008; Brainerd, Stein, et al., 2008), emotionally valenced stimuli favor gist connections more than neutrally valenced ones. Moreover, gist connections are responsible for false memory formation, thus, it follows that an enhanced emotional impact of studied items should boost memory errors. It could be argued that children with NLD, as more emotionally involved in events than the other groups, had a higher tendency to establish gist connections for emotional events. According to the associative-activation theory (Howe, 2005, 2008), the nonpresented items that are semantically connected with studied items are activated, at encoding, to a higher extent than non-semantically related ones. When emotionally charged items are activated in memory, there is an enhanced probability that related negatively charged information will be incorporated in false recollection (Howe et al., 2010); this seems particularly true for recognition tasks and may thus explain our findings of enhanced false recognition rates for causal errors in the group of NLD children. We note that our finding is specific for inferential causal errors and not for gap-filling errors. Indeed, non-presented causal scenes were tightly bound to the emotional content of the experienced effect, whereas non encountered script-consistent information was only indirectly influenced by the emotionality of the action effects. Children with NLD have been found to manifest more depressive symptoms than other learning disabilities (Bender et al., 1999; Spreen, 2011), thus the current data may be explained also taking into account the ‘‘mood-congruent effect’’ perspective. The available research on the effect of clinical depression on false memories points out that individuals with depressive symptoms tend to incorporate more negatively valenced non-experienced events into their memories than neutral ones (e.g., Howe & Malone, 2011). In the current study we only included negative events and therefore we cannot exclude that the pattern of errors of children with NLD would be different with emotionally charged, but positive events. It must be noted that for a number of reasons, including the ability to use an already validated paradigm, and avoiding possible confusion due to the combination of different types of emotional events, in the present study we only examined the emotionally negative effects (contrasted with neutral events). This allows our research to inform real world applications, such as the eyewitness context. Children who are asked to provide allegations in the courtroom are primarily prompted to recall negative events. Nevertheless, future research should also investigate whether children with NLD are more vulnerable to emotional events overall (including positive ones), or whether their proneness to memory illusions is specific to negative situations. In conclusion, our study offers important insights on memory for everyday actions in children with learning disabilities. In particular, the present findings showed that recognition memory can equal that of typically developing children, but their false recognition differs. This can be useful for understanding both the characteristics of memory distortions and the abilities of children with LD. Indeed, our results offer important implications both for educational and forensic contexts, as they show that different groups of LD may produce different patterns of memory errors. Even though further investigations with larger samples and different memory paradigms are needed, children with NLD have been found to be particularly vulnerable to emotional content and thus biased in attributing negative effects to unseen causes. Acknowledgment We thank Julia Ross for editorial assistance in the preparation of this manuscript.
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