To our knowledge, this is the first RCT involving two-year-olds designed to assess effects of an intervention ingredient on social development. We compared change in self-initiated socially engaged behavior in two groups receiving comparable treatments, differing only in the presence or absence of a supplementary social curriculum targeting SEI, IJA, and SPA, which are core deficits of autism. The test of SEI, IJA, and SPA outcome was stringent, reflecting generalization of these behaviors to a novel interaction context (location and materials), with an unfamiliar examiner, under unfamiliar circumstances (activity). Significant treatment effects were found for SEI at follow-up, with a trend toward significance for IJA at post-test and follow-up. Moderate effect sizes for SEI and IJA provide preliminary evidence for the efficacy of this intervention where a supplementary curriculum for social initiation and socially synchronized engagement in toddlers is overlaid on an existing group-based comprehensive intervention. A trend toward significance was found for greater improvement in the secondary variable of nonverbal cognition within the IS group during the intervention period. Trends toward significance for IJA and nonverbal cognition should be interpreted with caution since the joint tests for intervention differences was not significant for these outcomes. Secondary analyses also revealed social, cognitive, and language gains in both groups, particularly during the 6-month intervention period and within the IS group.
Our findings provide insights into the plasticity of social and communication development in toddlers with ASD. The supplementary curriculum activated development of socially engaged imitation (a greater than two-fold increase from pre- to post-test) that generalized across people, location, and interaction context. While others have reported improvements in imitation performance following targeted instruction (Ingersoll & Schreibman, 2006
), this is the first study to identify a targeted treatment response involving gains in the integration of imitation with socially directed gaze. Such ability enables toddlers with ASD to liken themselves to peers while also signaling their interactive engagement. This could foster a cascade of events in which toddlers with ASD draw increasing social, play, and language learning opportunities to themselves. Future research is needed to determine whether toddlers with ASD who develop SEI learn more efficiently or implicitly within other domains of development since imitation is a vital avenue through which language and play learning occurs (Ingersoll & Schreibman, 2006
; Speidel & Nelson, 1989).
The finding that both groups made significant gains over time in primary as well as secondary outcomes is of interest. The absence of more robust between-group differences is likely attributable to the similarity between the rival interventions. Instructional strategies for both interventions emphasized self-initiated communication, child choice, motivating learning materials and activities, joint action routines, natural reinforcers, and play-based learning activities. Some of these strategies are vital ingredients for development of flexible and generative language in typically developing children (Barsalou, Breazeal, & Smith, 2007
; Booth & Waxman, 2002
). In addition, the AEPS curriculum includes imitation and joint attention goals, albeit in less detail than in the IS curriculum. The high level of child-other engagement within the ecologically valid learning contexts of both interventions may have been sufficient to activate a high level of affect sharing and joint attention even without the additional infusion of instruction targeting joint attention and affect sharing. Indeed, Kasari et al. (2008) reported significant gains in joint attention behavior in preschoolers with ASD regardless of whether they received instruction focused on symbolic play or joint attention. Kasari et al.’s (2008) and our findings indicate that development of IJA and affect sharing may be stimulated through targeting interactions involving a joint focus of attention within motivating activities where children’s self-generated initiation is targeted. Our finding that slopes became less steep in the IS group or decreased in the Non-IS group during follow-up suggests the need for ongoing intervention targeting social development, and possibly that the community-based interventions did not sufficiently address these aspects of development. It also indicates that the IS group did not lose the skills acquired during the intervention. Further research is needed to understand more about the intervention ingredients that stimulate social development in toddlers with ASD, and to identify characteristics of children who show limited social improvement.
The gains in our participants’ expressive language and nonverbal cognitive functioning are encouraging. Since we did not include an “assess and monitor” control group, we cannot conclusively infer that these gains were effected by the overall intervention program common to both groups. However, there is indirect evidence for the intervention’s developmental impact. First, the most rapid growth in development occurred during the 6-month active intervention period.
The second source of indirect evidence is found in other published reports. In Dawson and colleagues’ (2009)
RCT involving 2-year-olds with ASD receiving either 20 hours per week of 1:1 home-based Early Denver Model intervention or referral to community intervention providers, gains in MSEL EL and VR T scores for the Early Denver and community intervention groups, after one year of intervention, were nearly identical to gains observed in our IS and Non-IS groups, respectively, from pre-test through follow-up (measured 6 months after the termination of treatment) on these same variables. Although Dawson and colleagues did not include social variables comparable to those reported herein, the expressive language and nonverbal cognition results from their study and ours indicate that toddlers with ASD are able to make substantial gains in early intervention using well-defined responsive instructional strategies and developmentally-based curriculum. Furthermore, our data indicate that such gains may be effected in a relatively brief period of time. Numerous intervention studies involving preschoolers with ASD have also reported gains in nonverbal cognition and language (reviewed by Rogers & Vismara, 2008
); these aspects of development may be particularly plastic and responsive to early intervention.
The present study contributes to a small body of literature focused on core deficits of communication and social functioning in young children with autism. Given the pervasive nature of imitation, joint attention and affect sharing deficits in most young children with ASD (Kasari, Freeman, & Paparella, 2006
; Landa et al., 2007
; Sullivan et al., 2007), and given that early social development is a major predictor of outcome for children with ASD (Charman et al., 2003
; Sigman & Ruskin, 1999
), there is a vital need to extend the research on which we report here. Future research should include a focus on whether and how an intervention such as the one reported here might impact parent-child interaction, and thus, mediate intervention effects.