The results of this study indicate that autism and Down syndrome often affect a young child’s joint engagement experiences during social interactions with a caregiver. Compared to typically developing peers, children with autism rarely coordinated attention to a shared object and the partner, a deficit that was no less marked in children who had acquired relatively large vocabularies. In contrast, children in the DS group readily shared events with their partners but they were less likely to attend to symbols during these periods. It is noteworthy that the influence of diagnosis on the form of joint engagement was remarkably stable over time. The low amount of coordinated joint engagement in children with autism and of symbol-infusion in children with Down syndrome was evident both when comparisons were made at 30 months, an age when both coordinating attention and symbol use are typically consolidated, and in comparisons when children had comparable expressive vocabularies. Furthermore, when the developmental course was plotted for a year (beginning when children with autism and with Down syndrome averaged 31 and 30 months of age, respectively, and TD children were 18 months of age, so that language abilities were comparable), coordinated joint engagement did not emerge in autism and symbol-infused joint engagement developed much less strongly for the children with Down syndrome.
These findings elaborate prior reports of early joint attention skill deficits that characterize autism and of the expressive language problems that challenge children with Down syndrome by providing a rare view of the development of joint engagement and symbol use during the optimizing setting of uninterrupted play with a caregiver. The Communication Play Protocol provided a standard premise that allowed us to observe the child in different communicative contexts and time. Children were almost always engaged with objects and/or people during the Play; even children with autism who were more likely unengaged than typically-developing children or children with Down syndrome, were on average engaged 85% of the 30 minute long observation period. Nevertheless, some communicative contexts were more difficult than others for toddlers with autism, who were most often unengaged during commenting contexts, and for toddlers with Down syndrome, who were most often engaged during interacting contexts. These context differences, which were not apparent in the typically-developing sample, suggest that it is important to consider not only how a disorder may impact forms of joint engagement but also how it may impact a child’s willingness to become engaged in interactions that focus on specific functions such as commenting and requesting.
This view supports three related conclusions. First, there are striking variations in the developmental path of symbol-infused joint engagement. Second, along some of these paths, coordinated joint engagement may be neither a necessary nor a sufficient step towards the introduction of symbols into parent-child interactions. Finally, and most intriguingly, across all of the groups in this study, periods of symbol-infused supported joint engagement during caregiver-child interactions may provide an especially facilitative context for early language learning.
With regards to developmental paths, we found two variations from the path taken by typically-developing toddlers where the consolidation of a triadic arrangement of attention between self, partner, and shared objects occurred before symbols infuse social interactions (Adamson et al., 2004
). The first variation was marked by the achievement of a triadic nonverbal communication structure that was not followed rapidly by the emergence of symbol infused joint engagement. A substantial portion of the group of young children with Down syndrome we observed had not started to infuse symbols regularly into joint engagement by age 2½, although all did do so at least minimally at some point during our year-long observation period. A similar pattern of coordinated joint engagement without symbol-infusion has been observed in a study of deaf 22 month-olds interacting with their hearing mothers (Prezbindowski, Adamson, & Lederberg, 1998) and in an on-going study of young children with severe speech and developmental delays prior to effective parent-implemented language intervention (Romski, Adamson, Bakeman, & Sevcik, 2007
). Taken together, these findings suggest that a certain level of vocabulary, and perhaps more generally “symbol-mindedness” (DeLoache, 2002
), are needed for a child to actively infuse symbols into joint engagement. Not surprisingly, infusing symbols into joint engagement depended on current verbal skill. Minimally verbal children, be they typically-developing but late talking 18-month olds (Adamson et al., 2004
) or 30 month old children with autism or with Down syndrome, were rarely observed in symbol-infused engagement states. Further, children who became verbal during our year-long study also became increasingly able to infuse symbols into joint engagement. But the abstraction of this pattern of delay also underscores the need for research that more fully explores the specific barriers to symbolization faced by young children with Down syndrome (Yoder & Warren, 2004
) and other children who have mastered the rudiments of coordinated joint engagement.
The second variation in the typical developmental path involves a movement towards increased symbol infusion without the consolidation of coordinated joint engagement either before or during the emergence of symbol-infused joint engagement. This pattern was more likely to characterize children with autism (for whom symbol-infused joint engagement occurred more often than coordinated joint engagement in 52% of the participants) than in either the typically-developing or Down syndrome samples (for whom symbol-infused joint engagement occurred more often than coordinated joint engagement in only 17% and 10% of the participants, respectively). There are a myriad of reasons why young children with autism might have difficulty sustaining periods of coordinated joint engagement even when interacting with a caregiver who was trying to facilitate communication. The child may appear uninterested in the partner (Osterling & Dawson, 1994
), or fail to orient to her (Dawson, Meltzoff, Osterling, Rinaldi, & Brown, 1998
; Leekam & Moore, 2002) and be affectively unresponsive (Joseph & Tager-Flusberg, 1997
; Hobson, 1993
). Highly restricted or idiosyncratic object interests may also make it difficult to locate a topic for sustained shared attention (Williams, Costall, & Reddy, 1999
) and conversation (Watson, 1998
). Moreover, the child might have difficulty integrating elements during the rapid flow of a social interaction, and thereby fail to alternate gaze between a partner’s face and an object, (e.g., Charman, 2004
), coordinate an emotional response to an object and gaze to a partner, or produce a well-timed declarative point (Travis & Sigman, 2001
Alongside these findings of difficulty with coordinated and with symbol-infused joint engagement, it is particularly noteworthy that young children with autism and with Down syndrome were often able to sustain periods of supported joint engagement at a rate comparable to that observed in typically-developing 18- and 30-month old children. This rate was usually substantial; on average, children spent approximately half of each 30 minute communication play in supported joint engagement. Moreover, in all of the three groups, supported joint engagement was as likely as coordinated joint engagement to be infused with symbols. Thus even children with autism who found coordinated joint engagement problematic could enter a sphere of shared focus in which partners’ actions blend with their own. Furthermore, even children with Down syndrome, who were less likely than others to engage in solitary object play, often shared objects without simultaneously coordinating attention to their partner.
Certainly much of the credit for negotiating supported engagement states accrues to the caregivers, especially when their partner is a child with autism who rarely acknowledges bids for joint attention and who might even actively try to thwart them (Adamson et al., 2001
). Although there are yet few studies that focus on the caregiver’s contribution to children’s engagement states, there is evidence that parents interacting with children with autism or with other developmental disorders may synchronize their actions with the child’s actions at the same rate as parents interacting with a typically developing child (Siller & Sigman, 2002
), and that they may modify their actions in ways that increase the salience of objects by, for example, supplementing words and pointing gestures with more literal acts such as banging and waving (Baranek, 1999
; McArthur & Adamson, 1996
). Moreover, evidence is mounting that parents may implement interventions that promote joint attention in toddlers with autism (e.g., Schertz & Odom, 2007
Nevertheless, it is also important to appreciate the child’s contribution. For a period to be coded supported joint engagement, a child, as well as his or her caregiver, had to be actively involved in object or event sharing. Given our coding scheme’s criteria, this meant that the child was not merely watching the caregiver (which would have been coded as on-looking) and that he or she sustained attention to a shared topic for at least 3 seconds (fleeting interest would have been coded unengaged). Thus, supported joint engagement indicates that the child had at least a nascent capacity to move beyond a singular focus on objects to share objects in a way that incorporates a partner’s contribution, however implicit and unappreciated and however dependent on extraordinary scaffolding.
Most intriguingly, in all three groups, variations in how often children were observed in symbol-infused supported joint engagement predicted the growth of their receptive and expressive vocabularies, after controlling for initial language level. These findings about the significance of periods of symbol-infused supported joint engagement converge well with mounting evidence that periods of time when a language learning child focuses primarily on an event and its symbolic representation, rather than on the full triad of partner, object, and symbol, may be especially conducive to new word learning. For example, Bloom (1993
; Bloom & Tinker, 2001
) presents compelling evidence that arrangements that lessen the cognitive and affective demands of interpersonal communication and heighten the relation between symbol and referent may help a child focus on the difficult task of acquiring language. Early language acquisition seems to be facilitated when mothers follow their child’s lead rather than direct their child’s attention (Tomasello & Farrar, 1986
). Moreover, children’s ability to respond to joint attention bids, rather than their ability to initiate them, has often been found to predict variations in early language learning in young children, including within samples of children with autism (Bono, Daley, & Sigman, 2004
; Sigman & Ruskin, 1999
; Siller & Sigman, 2002
; Sullivan, Finelli, Marvin, Garrett-Mayer, Bauman, & Landa, 2007
; cf. McDuffie et al., 2005
By the end of the study, all of the typically developing children, 78% of the children with autism, and 79% of the children with Down syndrome had acquired at least a 50 word expressive vocabulary. These rates, especially for children with autism, are relatively high compared to older estimates (Tager-Flusberg, 1994
; cf. Lord et al., 2004
). Since the children with autism participated in early intervention programs, their success may underscore the promise of early detection and intervention (Landa, 2007
; Wetherby & Woods, 2006
), although it may also reflect changes in diagnostic criteria over time. We hasten to add that our findings do not indicate that periods of symbol-infused coordinated joint engagement are unimportant to language acquisition. Focusing only on the symbol-referent relationship during supported joint engagement may not provide a young child with the information about meaning that is gained when toddlers monitor their partner’s attention and intentions (Baldwin, 1995
). Periods of coordinated joint engagement may provide a particularly rich context for toddlers to learn about theory of mind specifically (P. Nelson, Adamson, & Bakeman, in press
) and about how to participate in the decontextualized, connected conversations that typically emerge during the preschool years (Adamson & Bakeman, 2006
; Nelson, 1996
). Thus even if children with autism acquire language, they may continue to experience problems using it appropriately in conversations (Tager-Flusberg, 1994
), and they may display a peculiar fascination with symbol systems such as letters, numbers, and names outside the sphere of joint engagement (Frith, 1989
These findings highlight the importance of looking beyond periods of coordinated joint engagement to study the way additional arrangements of attention might allow children to engage in language-facilitating interactions, including children with impaired joint attention skills and those who find the step into the symbolic sphere especially challenging. This contention affords with the growing appreciation (articulated well in Akhtar, 2005
; Hoff, 2005
) that although all typically developing children develop joint attention skills and language, not all cultures embed early object exploration or first words in a child-centered social context. Moreover, these findings encourage us to continue to study the transaction between children and their partners at various points along the path of communication development in hopes of understanding more fully how others may provide scaffolds that facilitate a child’s symbol formation and use.