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Journal of Intellectual Disability Research 891

volume 59 part 10 pp 891 –901

OCTOBER

doi: 10.1111/jir.12191 2015

Joint attention behaviours and vocabulary development in children with Down syndrome L. Zampini, A. Salvi & L. D’Odorico* Department of Psychology, University of Milano-Bicocca, Milan, Italy

Abstract Background Because of their difficulties in language development, various studies have focussed on the precursors of linguistic skills in children with Down syndrome. However, data on the predictive role of joint attention on language development in this population are inconsistent. The present study aimed to analyse attention behaviours in a group of children with Down syndrome. The existence of both concurrent and longitudinal relationships between joint attention and vocabulary development was investigated. Method The participants were 18, 24-month-old, Italian children with Down syndrome. The children’s attention skills were assessed during semistructured free-play sessions in interaction with their mothers. A nominal exhaustive scheme was applied to code the children’s behaviour. Moreover, the children’s vocabulary development (both receptive and expressive) was assessed with the Italian version of the MacArthur-Bates Communicative Development Inventory at both 24 and 30 months. Results Data analyses showed that children with Down syndrome spent a large part of the interactive play session in joint attention situations. Moreover, the children’s behaviour of proposing a joint attention focus to their communicative partners appeared Correspondence: Dr Laura Zampini, Department of Psychology, University of Milano-Bicocca, Piazza dell’Ateneo Nuovo, 1 20126, Milan, Italy (e-mail: [email protected]). * Unfortunately, Professor Laura D’Odorico passed away after the submission of this paper

to be a significant predictor of the children’s vocabulary comprehension skills as assessed 6 months later. Conclusions These results support the hypothesis of continuity between preverbal precursors and vocabulary development in a population with atypical development. Keywords Down syndrome, joint attention, predictive index, vocabulary development

Introduction Joint attention behaviours are defined by Baldwin (1995) as those episodes in which a child and an adult are focussed on the same object, and the participants are both aware that the attentional focus is shared. Joint attention has an important role in the development of communication skills (Bruner 1975). In particular, as suggested by Tomasello & Todd (1983), the way mothers and children regulate each other’s attention affects children’s early vocabulary development. An explanation of the relationship between joint attention and vocabulary involves the referential role of joint attention: often, the adult labels the object of common interest in the context of joint attention. Therefore, joint attention may help the child in the association of names and objects because the field of possible referents becomes limited to the elements of the environment to which the child is attending (Harris et al. 1996). Many studies have investigated the predictive role of joint attention behaviours on vocabulary develop-

© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

volume 59 part 10 october 2015

Journal of Intellectual Disability Research 892 L. Zampini et al. • Joint attention in children with Down syndrome

ment. For instance, Carpenter et al. (1998) found that the amount of time spent by children in joint engagement at 14 months was significantly correlated with both 18- and 24-month productive vocabulary size. Moreover, Morales et al. (2000) found that for a group of 52 6-month-old infants, the capacity to match their mother’s direction of gaze was related to the children’s vocabulary development at 12 months. In their review on the relationship between joint attention and vocabulary development, Akhtar & Gernsbacher (2007) noted that joint attention can be initiated by the caregiver or by the child. In some situations, the child responds to the communicative signals given by the adult; in other situations, the child proposes a new focus of joint attention. In the first case, the child must demonstrate the competence to follow the adult’s attention prompt, whereas in the second case, the child must be able to produce the communicative signals necessary to involve the attention of the adult in a specific object of interest. To respond to a joint attention bid, the child must be able to follow the adult’s gaze (see Brooks & Meltzoff 2005), understand and follow deictic communicative gestures (e.g. pointing to or showing an object), or understand a verbal comment on a specific object. To propose an attentional focus, the child must be able to produce communicative signals using gazes, gestures or words. The propensity to initiate joint attention and the propensity to follow an attentional focus have different outcomes on children’s vocabulary development. Some studies (Desrochers et al. 1995; Mundy et al. 1995) found that the ability to follow the adult’s attentional focus (e.g. following the adult’s gaze or pointing) was related to the vocabulary development of typically developing children. Moreover, Morales et al. (2000) found that the ability to respond to joint attention at 6, 8, 10, 12 and 18 months was positively related to individual differences in vocabulary development at 30 months in typically developing children. However, it has to be noted that, in the same study, the ability to respond to joint attention at 21 and 24 months was not related to the children’s vocabulary development at 30 months. In contrast, other studies found that children’s vocabulary comprehension was facilitated during

interactions in which the caregiver followed rather than led the child’s attentional focus. For instance, in an experimental task of new-word learning, Dunham et al. (1993) found that in a group of 18-month-old typically developing children, those who were required to switch their attention from one focus (i.e. a toy) to another (i.e. the target object with an unknown name) were less likely to learn new words. The propensity to redirect the children’s attention could also have effects on the children’s lexical acquisition style; in fact, Tomasello & Todd (1983) showed that children who have mothers that frequently initiate interactions by redirecting their children’s attention learn fewer object labels, but more personal–social words. Other studies (e.g. Uvlund & Smith 1996; Mundy & Gomes 1998) found that the ability to both follow and propose an attentional focus were related to children’s vocabulary development. In a group of 24 children ranging in age from 14 to 17 months, Mundy & Gomes (1998) found that the ability to initiate joint attention bids was a significant predictor of expressive language, whereas the ability to respond to joint attention bids was a significant predictor of receptive language. Moreover, Uvlund & Smith (1996) found that the ability to both follow attentional signals and to propose a new attention focus were connected with receptive and expressive language in a sample of children with birthweight below 1501 gms. Joint attention behaviours have also been investigated in children with atypical development, such as children with visual or hearing impairments (e.g. Prezbindowski et al. 1998; Bigelow 2003), and in children with intellectual disability (e.g. Paparella & Kasari 2004). This study focuses on attention behaviours, particularly joint attention episodes, in a specific population: children with Down syndrome. Down syndrome is a genetic condition caused by the presence of an extra chromosome 21 (or at least part of it). This condition is usually associated with psychomotor delays and cognitive impairments. Moreover, the language development of children with Down syndrome is usually particularly impaired (Abbeduto et al. 2007; Zampini & D’Odorico 2013), and the discrepancy between language comprehension and production is wider than in typically developing children (Caselli et al. 1998).

© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

volume 59 part 10 october 2015

Journal of Intellectual Disability Research 893 L. Zampini et al. • Joint attention in children with Down syndrome

Because of their difficulties in language development, various studies have focussed on the precursors of linguistic skills in children with Down syndrome. Vocal (e.g. Steffens et al. 1992), gestural (e.g. Zampini & D’Odorico 2009) and attentional (e.g. Kasari et al. 1995) indices have been considered. For instance, with regard to gestural indices, gesture production at 24 and 36 months of chronological age appeared to be a reliable predictor of later vocabulary size in children with Down syndrome (Zampini & D’Odorico 2011). With regard to attention behaviours, some specific problems have been identified in children with Down syndrome. As found by Legerstee & Bowman (1989), children with Down syndrome showed a 2-month delay in the ability of distinguishing between people and objects, that is an important prerequisite for the development of joint attention (Gelman & Spelke 1981); typically developing children usually show differential responsiveness to people and objects at 2 months, whereas children with Down syndrome show this ability only at 4 months (Legerstee & Bowman 1989). Moreover, Legerstee & Weintraub (1997) found that children with Down syndrome (with a developmental age ranging from 6 to 20 months and a chronological age ranging from 12 to 26 months) produced less coordinated attention than typically developing children matched for developmental age, although the ability to establish joint attention formats increased with development in children with Down syndrome. Moreover, Kasari et al. (1995) found that children with Down syndrome (ranging in chronological age from 13 to 42 months), compared with typically developing children matched for developmental age (from 9 to 27 months), exhibited less shifting of attention between the caregiver and the object of common interest. However, in this study, no differences were found in the number of coordinated joint attention situations that occurred in both groups of children. Considering the distinction between proposing and following a joint attentional focus, Landry & Chapiesky (1989) found that 12-month-old children with Down syndrome were less responsive when their mothers attempted to redirect their attention than when their mothers followed their attentional focus. A possible explanation for this result is that diverting the child’s attention and shifting his/her

attentional focus to something else may overload the child’s cognitive skills (Landry & Chapiesky 1989). With regard to the relationships between attention behaviours and language development in children with Down syndrome, only a few studies have specifically aimed to evaluate the linguistic outcomes of joint attention behaviours in this population (e.g. Harris et al. 1996; Adamson et al. 2009). Moreover, the results in the literature are inconsistent, and there is no clear evidence of the role of joint attention behaviours in predicting vocabulary outcomes of children with Down syndrome. For instance, Adamson et al. (2009) did not find a relationship between joint attention behaviours and vocabulary development in children with Down syndrome. In fact, these children did not reach an adequate level of language development (i.e. they had significantly lower scores on both receptive and expressive vocabulary tests) even if they did not differ from chronologically age-matched typically developing children in the proportion of time spent in joint engagement. Moreover, Harris et al. (1996), coding a 5-min free-play episode for each child– caregiver dyad, found that the number of joint attention episodes demonstrated by a group of 24-month-old children with Down syndrome was not related to their language development as assessed 13 months later. However, in the same study, the authors found that the frequency with which the caregivers maintained their children’s attentional focus was positively related to the children’s level of language comprehension (as assessed by the Reynell Developmental Language Scales), whereas the frequency with which the caregivers redirected their children’s attentional focus, from an object selected by the child to another object, was negatively associated with the children’s receptive language skills. Because data on the predictive role of joint attention in children with Down syndrome are inconsistent, the present study aimed to analyse attention behaviours in a relatively large and homogeneous group of children with Down syndrome. In fact, the high variability in participants’ chronological or developmental age is a limitation of many studies on this topic (e.g. Kasari et al. 1995; Legerstee & Weintraub 1997), because it does not allow to compare children at the same level of experience or

© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

volume 59 part 10 october 2015

Journal of Intellectual Disability Research 894 L. Zampini et al. • Joint attention in children with Down syndrome

development. In the present study, the individual differences in attention behaviours of 24-month-old children with Down syndrome were considered. Moreover, the existence of concurrent and longitudinal relationships between joint attention and vocabulary development, both receptive and expressive, was investigated. As attention regulation has been found to be specifically related to vocabulary development in typically developing children (e.g. Carpenter et al. 1998; Morales et al. 2000), we decided to assess children’s receptive and productive vocabulary and not their general receptive and expressive skills as done in previous studies (e.g. Kasari et al. 1995; Harris et al. 1996). In summary, the present study aimed to analyse the proportion of time spent in joint attention behaviours by 24-month-old children with Down syndrome and the concurrent and longitudinal relationships between joint attention behaviours and the children’s receptive and expressive vocabulary, as assessed at 24 and 30 months.

Methods Participants For the present study, 18 children with Down syndrome (13 females and 5 males) were recruited. Their mean chronological age was 24 months [standard deviation (SD) = 0.76; range = 24–26 months]. All of the participants were attending a monitoring programme on language development in children with Down syndrome at the Department of Psychology of the University of Milano-Bicocca. All of the children had free trisomy 21 and normal or corrected-to-normal visual and auditory skills. The children’s mean developmental age, as assessed by the Brunet–Lézine Scale of Psychomotor Development (Brunet & Lézine 1967), was 16 months (SD = 2.39; range = 11–19 months). Data on the developmental age of 24-month-old children with Down syndrome are in line with those of previous studies (Galeote et al. 2008; Zampini & D’Odorico 2013).

Procedure The method used in the study has been reviewed and approved by the ethical board of the University

of Milano-Bicocca. Moreover, all the children’s parents signed a written consent. To assess the children’s attention skills, mothers and children were observed during semi-structured free-play sessions. For each child, a 20-min videorecorded session was conducted. A standardised set of toys was given to each child; the toys were introduced in a specific order: a farm set, a plastic phone, four illustrated books and a doll with a nurturing set. A new toy was introduced approximately every 5 min, but the mother–child dyad could freely play with everything presented. The mothers were encouraged to play with their children as usual. The sessions took place in the Infant Observation Laboratory of the Department of Psychology of the University of Milano-Bicocca. After the observation session, the children’s vocabulary size, in both comprehension and production, was assessed by administering the Italian version of the MacArthur–Bates Communicative Development Inventories (Il Primo Vocabolario del Bambino – PVB; Caselli & Casadio 1995) to their parents. The validity of the MacArthur–Bates Communicative Development Inventories in children with Down syndrome has been demonstrated by Miller et al. (1995) for English-speaking children and by Zampini & D’Odorico (2009) for Italianspeaking children. The PVB consists of two different forms: one for young children between the ages of 8 and 17 months, and one for toddlers ranging in age from 18 to 36 months. Because of the impairment in language development that typically occurs in children with Down syndrome, the first form of the inventory was used. In fact, as reported by Zampini & D’Odorico (2012, 2013), 24-month-old Italian children with Down syndrome have a mean productive vocabulary size of less than 10 words. The first form of the inventory, called Gestures and Words, includes a vocabulary list of 408 words to assess both vocabulary comprehension and production and a section to assess gesture production. For the purpose of the present study, we only considered vocabulary comprehension (PVB word comprehension) and production (PVB word production) by noting the number of words marked by the parents on the inventory. Word comprehension and production were further assessed in the same manner 6 months later, when the children were 30 months old, to assess

© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

volume 59 part 10 october 2015

Journal of Intellectual Disability Research 895 L. Zampini et al. • Joint attention in children with Down syndrome

24 months

PVB word comprehension PVB word production

30 months

M

SD

Range

M

SD

Range

173.06 8.83

83.28 5.31

44–341 0–21

244.17 22.44

78.82 18.67

77–351 2–85

Table 1 PVB word comprehension and production at 24 and 30 months

PVB, Il Primo Vocabolario del Bambino; SD, standard deviation.

their vocabulary increase. Descriptive data on PVB word comprehension and production at both sessions are reported in Table 1.

Coding and measures To assess the children’s attention behaviours, the observation sessions were coded through a nominal exhaustive coding scheme adapted from the scheme developed by Bakeman & Adamson (1984). To make the scheme exhaustive, the categories ‘attention getting’ and ‘not codable’ (described later) were added. The following categories were used: 1 Disengagement. Situations in which the child is not involved with any person or object (e.g. the child is walking around the room; the child is staring at the door). 2 Observation of other people actions. Situations in which the child is observing the actions of another person. The child is not participating in this action, and the adult is not attempting to involve the child in the action (e.g. the child is observing his/her mother while she is going to take an object). 3 Interaction with a person. Situations in which the child interacts exclusively with a person without using any object (e.g. the mother and the child are singing a song or speaking about something that is not present in the context). 4 Interaction with objects. Situations in which the child interacts exclusively with an object without paying attention to the adult. The adult is not paying attention to the child or to the object (e.g. the child is playing with a toy car while the mother is reading an illustrated book). 5 Passive attention. Situations in which the child and the adult are involved with the same object, but the child is not considering the presence of the

other person (e.g. the mother and the child are playing with a toy car, but the child is not looking at his/her mother and is not responding to her requests). 6 Attention getting. Situations in which the child is attempting to attract the adult’s attention to an object (e.g. using gaze, gestures, vocalisations or words), but the adult does not respond to the child’s request for attention (e.g. the child is pointing at pictures in a book, but his/her mother continues reading without considering the communicative effort of the child). 7 Joint attention. Situations in which the child interacts with both the adult and an object. We can infer that the child is recognising the presence of the other person considering the use of gaze, the production of communicative gestures, or the production of vocalisations or words. According to the definition of Tomasello & Farrar (1986), two criteria are necessary to code an episode as joint attention: (1) it must last at least 3 s; and (2) three elements – a child, an object, and an adult – must be identified in the episode. The joint attention episodes were further divided into two categories: ‘joint attention follow focus’ and ‘joint attention propose focus’. • Joint attention follow focus. Situations in which the child follows the attention focus proposed by the adult. The child can understand and appropriately respond to the communicative signals produced by the adult (e.g. the child looks at his/ her mother’s face and then at the object at which his/her mother is looking; the child looks in the direction indicated by his/her mother; the child produces a vocalisation as an answer to a maternal comment on an object). • Joint attention propose focus. Situations in which the child introduces a new attentional focus. The

© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

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Journal of Intellectual Disability Research 896 L. Zampini et al. • Joint attention in children with Down syndrome

child can produce adequate communicative signals to share interest in a specific object or situation (e.g. the child shows an object to his/her mother; the child points at something in a declarative way). 8 Not codable. Situations in which the child is not captured by the camera or it is not clear on the video what the child is doing. An interval coding strategy was used in which each observation session was divided into 5-s intervals, and a code was given to each interval (considering the behaviour that fills the greatest proportion of time in each interval). An interval coding scheme has been preferred to an event-based one because it was really difficult to identify with precision the exact instant of beginning and ending of each attention behaviour. After coding the observation sessions, the frequency of each behavioural category on the total of the intervals coded was computed. The intervals coded as Not codable were not considered in the total number of intervals.

Reliability Inter-coder reliability was assessed in 20% of the observation sessions. A second observer coded four randomly selected sessions. Disagreements were resolved by referral to a third observer. The mean percentage of agreement was 85% of the intervals. As the target variables of the study are joint attention behaviours, a mean percentage of agreement has been separately computed on the intervals coded as joint attention. The mean percentage of agreement was 89% on the intervals coded as joint attention follow focus, and 85% on the intervals coded as joint attention propose focus.

Results Description of the children’s attentional behaviours Data deriving from the coding of the observation sessions showed that 24-month-old children with Down syndrome spent a large amount of time in joint attention episodes. As shown in Table 2, the mean frequency of intervals coded as joint attention was higher than 50% of the intervals. Although the

Table 2 Proportion of time spent by children on each attentional behaviour

Disengagement Observation Interaction with a person Interaction with objects Passive attention Attention getting Joint attention (JA) JA follow focus JA propose focus

M

SD

Range

0.05 0.02 0.06 0.18 0.11 0.01 0.59 0.45 0.14

0.05 0.02 0.05 0.10 0.04 0.01 0.12 0.13 0.11

0.00–0.14 0.00–0.06 0.00–0.18 0.04–0.33 0.03–0.19 0.00–0.02 0.39–0.81 0.22–0.74 0.02–0.47

SD, standard deviation.

range of intervals coded as joint attention among the children was wide (0.39–0.81), it should be noted that each 24-month-old child with Down syndrome spent at least 39% of the observation session in joint attention situations. Moreover, on average, only 5% of the intervals were coded as disengagement, meaning that the children were active participants in the interaction session.

Concurrent and longitudinal relationships between joint attention behaviours and vocabulary size With regard to the relationships between joint attention and vocabulary skills, no significant correlations were found between the proportion of time spent in joint attention behaviours and the number of words comprehended or produced by the children at 24 months (see Table 3). As PVB word comprehension (but not PVB word production) was significantly associated with children’s developmental age (PVB word comprehension: r = 0.599; P = 0.014. PVB word production: r = 0.245; P = 0.360), the relationships between joint attention behaviours and children’s receptive vocabulary were also computed controlling for developmental age. Results from partial correlations showed that the total amount of time spent by children in joint attention situations was significantly correlated with PVB word comprehension (r = 0.577; P = 0.024). No significant relationships were found between receptive vocabulary and the

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Journal of Intellectual Disability Research 897 L. Zampini et al. • Joint attention in children with Down syndrome

Joint attention (JA) JA follow focus JA propose focus

PVB word comprehension

PVB word production

At 24 months

At 24 months

r

P

r

P

0.42 0.16 0.27

0.079 0.529 0.282

−0.06 −0.19 0.15

0.804 0.455 0.545

Table 3 Pearson’s correlations between joint attention behaviours and PVB word comprehension and production at 24 months

PVB, Il Primo Vocabolario del Bambino; SD, standard deviation.

Table 4 Results of regression analyses on PVB word comprehension at 30 months

Model 1

R2

R2 adj

F (df)

0.79

0.78

60.11 (1,16)***

0.85

0.83

41.07 (2,15)***

Δ R2

PVB word comprehension at 24 months Model 2

β

0.89***

PVB word comprehension at 24 months Joint attention follow† Joint attention propose

0.06* 0.82*** −0.03 0.25*

* P < 0.05; *** P < 0.001. † Variables excluded. df, degrees of freedom; PVB, Il Primo Vocabolario del Bambino.

subcategories joint attention follow focus (r = 0.387; P = 0.154) and propose focus (r = 0.195; P = 0.485). To assess the predictive role of joint attention on the children’s subsequent receptive and expressive vocabulary, two hierarchical regression analyses were conducted to determine the contribution of joint attention behaviours to explaining the individual variability in children’s vocabulary comprehension and production at 30 months. In the first regression analysis, PVB word comprehension at 30 months was the dependent variable, and PVB word comprehension at 24 months and joint attention behaviours (both following and proposing focus) were entered as independent variables. To verify the unique contribution of joint attention on children’s receptive skills, PVB word comprehension at 24 months was entered first. As shown in Table 4, the children’s behaviour of proposing a focus of joint attention accounted for a significant part of the variance in the children’s receptive skills development. In the second regression analysis, PVB word pro-

duction at 30 months was the dependent variable, and PVB word production at 24 months and joint attention behaviours (both following and proposing focus) were entered as independent variables. In this case, to verify the unique contribution of joint attention on children’s expressive skills, PVB word production at 24 months was entered first. This analysis (see Table 5) showed that the number of words produced by the children at 30 months could not be predicted by either their joint attention behaviours or their word production at 24 months.

Discussion The present study aimed to examine attention behaviours in a group of 24-month-old children with Down syndrome. In particular, the relationships between joint attention and vocabulary development were considered. Data analyses showed that children with Down syndrome spent a large part of the interactive play

© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

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Journal of Intellectual Disability Research 898 L. Zampini et al. • Joint attention in children with Down syndrome

Model 1

R2

R2 adj

F (df)

0.11

0.05

1.95 (1,16)

PVB word production at 24 months† Joint attention follow† Joint attention propose†

β

Table 5 Results of regression analyses on PVB word production at 30 months

0.33 0.14 −0.27



Variables excluded. df, degrees of freedom; PVB, Il Primo Vocabolario del Bambino.

session in joint attention situations. On average, half of each observation session was spent in coordinated attention with the caregiver. In particular, the major part of the children’s joint attention behaviours consisted of situations in which the children followed the attentional focus proposed by their caregivers (on average, 45% of the observation session). Situations in which the children proposed a new attentional focus to their partners were less frequent (on average, 14% of the session), although each child (2–47% of the session) demonstrated the ability to produce the communicative signals necessary to involve the attention of their caregivers in specific objects of interest. The analysis of concurrent relationships between attention behaviours and language showed that there were no associations between the frequency of joint attention situations and both receptive and expressive vocabulary size. However, when controlling for children’s developmental age, the total amount of time spent in joint attention situations appeared to be significantly related to children’s receptive vocabulary. In contrast, considering the longitudinal associations between joint attention behaviours and vocabulary development, the results of the regression analyses showed that the receptive vocabulary development of children with Down syndrome could be predicted by both their vocabulary comprehension skills and joint attention behaviours at 24 months. In particular, PVB word comprehension at 30 months was mainly explained by PVB word comprehension at 24 months. However, the proportion of intervals at which the children proposed an attentional focus to their caregivers appeared to explain a significant part of the variance in receptive vocabulary development. Therefore, the behaviour of proposing a joint attention focus may be consid-

ered a significant predictor of the vocabulary comprehension skills of children with Down syndrome. To our knowledge, this is the first evidence of the existence of an association between joint attention skills of children with Down syndrome and their later receptive vocabulary size. The lack of association between situations in which the child followed the attentional focus proposed by the caregiver and the child’s vocabulary may be due to the cognitive load required to divert attention and focus it on something else (Landry & Chapiesky 1989). It is possible that this request for greater cognitive effort may overload the cognitive resources of children with developmental disabilities. Therefore, these children may have few residual resources to make a label-referent association in situations in which caregivers redirect their attentional focus. Moreover, it has to be noted that the findings of the present study shifted the perspective from the caregiver to the child with Down syndrome: in Harris et al.’s (1996) study, the focus was on the caregiver’s ability to maintain attention on toys selected by the child, whereas in the present study, the focus was on the child’s ability to initiate bids for joint attention. Therefore, not only the caregivers’ responsiveness, but also individual differences in children’s attention skills are shown to have an effect on their vocabulary development. However, with regard to productive vocabulary, the results of the regression analyses showed that the variance in PVB word production at 30 months could not be explained by either the children’s joint attention behaviour or the children’s productive vocabulary size at 24 months. These data are in contrast to the results of Mundy & Gomes (1998), who showed that the ability to initiate joint attention bids appeared to be significantly associated

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Journal of Intellectual Disability Research 899 L. Zampini et al. • Joint attention in children with Down syndrome

with expressive language development in typically developing children. This difference may be explained in light of the specific problems of children with Down syndrome in language development, particularly verbal production. It is possible that a larger number of factors (e.g. phonological and articulatory skills) may explain the children’s competence in producing words.

Conclusions The results of the present study have both theoretical and practical implications. Theoretically, these results support the hypothesis of continuity between preverbal precursors and vocabulary development in a population with atypical development. A continuity between preverbal and verbal development in children with Down syndrome has been already shown considering gesture production, as communicative gestures appear to have a predictive role on children’s vocabulary development (e.g. Zampini & D’Odorico 2009). Therefore, it has to be underlined that typical patterns of language acquisition are also found in children with atypical development. Practically, these results suggest that the vocabulary skills of children with Down syndrome can be enhanced by engaging them in joint attention situations. In particular, it may be useful to suggest that the caregivers of children with Down syndrome follow the attentional focuses proposed by their children rather than redirecting their attention. This advice could be particularly useful in light of the results in the literature (Buium et al. 1974; Cardoso-Martins & Mervis 1985; Marfo 1990) showing that the mothers of children with Down syndrome use a more directive style when interacting with their children. Moreover, as the children’s ability to propose an attentional focus has been found to be related to their vocabulary development, a specific training to teach the children to initiate bids for joint attention could be useful for their language development. These kind of trainings, aiming to increase children’s propensity to initiate joint attention, have already been successfully used with children with autism (e.g. Taylor & Hoch 2008). However, it has to be noted that the population of children with Down syndrome and the population of children with autism are usually very

different in their communicative development. Therefore, more evidence from future studies is needed to plan appropriate clinical interventions.

Limitations and future directions The present study aimed to analyse joint attention behaviours in children with Down syndrome. A limitation of the study is the absence of a control group. In fact, the comparison with a group of typically developing children or with a group of children with intellectual disability of other aetiology could be useful to look at the specificities of children with Down syndrome. Future studies will address this topic. Another study limitation is that we did not examine the way used by children to involve their partners’ attention. Future studies will deeply investigate how children with Down syndrome involve the attention of their caregivers, using vocal and gestural communicative signals. Considering the predisposition of children with Down syndrome to use a high number of communicative gestures, particularly pointing gestures (Zampini & D’Odorico 2011), we would expect that these children will frequently use non-verbal bids to introduce a new attentional focus.

Acknowledgements This paper is dedicated to my great teacher, Laura D’Odorico, who passed away after the submission of the manuscript. I am grateful for everything she has taught me and for the passion that she has instilled in me.

Conflict of interest The authors report non conflict of interest.

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© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

volume 59 part 10 october 2015

Journal of Intellectual Disability Research 901 L. Zampini et al. • Joint attention in children with Down syndrome

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Zampini L. & D’Odorico L. (2009) Communicative gestures and vocabulary development in 36-month-old

Accepted 1 February 2015

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© 2015 MENCAP and International Association of the Scientific Study of Intellectual and Developmental Disabilities and John Wiley & Sons Ltd

Joint attention behaviours and vocabulary development in children with Down syndrome.

Because of their difficulties in language development, various studies have focussed on the precursors of linguistic skills in children with Down synd...
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