A Comparison of Toddlers with ASD and Typical Development: Relating Repetitive Behaviors, Early Social Communication Symptoms, and Nonverbal Skills

Background:
While repetitive and stereotyped behaviors (RSB) were once considered to be later developing symptoms of autism spectrum disorder (ASD), more recent research has found that RSB emerges during the toddler years.  Research examining the relationship between RSB and other early ASD symptoms (e.g., social communication, symbolic play) is limited, but emerging. More in depth research into this relationship will guide the development of intervention targets appropriate for very young children with ASD, and further the empirical understanding of early ASD symptomology. (Shumway & Wetherby, 2009). 
Objectives:
There were three objectives of this study: 1) to compare toddlers with ASD to mental age matched toddlers with typical development on early symptoms measured using the Communicative and Symbolic Behavior Scales (CSBS; Wetherby and Prizant, 2002). While previous research with the CSBS has compared toddlers with ASD and typical development matched on chronological age, we were interested in how mental age matched groups compare; 2) to compare how RSB differed across groups and how they relate to other early symptoms; and 3) to examine how early symptoms of ASD relate to nonverbal ability. 
Methods:
Thus far, participants include 7 18-36 month old boys with ASD (diagnosed using the ADOS) and 7 typically developing (TD) boys matched on mental age measured by the Mullen Scales of Early Learning (Mullen, 1992). Participants were administered the CSBS and composite scores were calculated.  Additionally, each behavior sample was scored and subsequently coded for RSB using the CSBS RSB Movement Scale (Wetherby and Morgan, 2007). Date collection is ongoing.
Results:
Thus far, toddlers with ASD received lower scores on the Social Composite (i.e., emotion and eye gaze, gestures, and communication rate/function) compared to children with TD, t(6) = 14.49, p <.0001.  Further, they received lower scores on the Symbolic Composite (i.e., use of objects, understanding of words), t(6) = 3.54, p<.01.  While there was a trend for toddlers with ASD to show lower scores on the Speech Composite (use of sounds, use of words), this was not significant in the current small sample, t(6) = 1.94, p<.10.  Further, CSBS scores were related to nonverbal mental age such that toddlers with ASD who had lower nonverbal abilities demonstrated  less social, symbolic, and expressive language skills, r(7) = .98, p<.01.  It is predicted that these early symptoms will be related to repetitive behaviors in toddlers with ASD.  RSB coding is ongoing and data will be available within a few weeks. 
Conclusions:
Thus far, toddlers with ASD showed less social skills, symbolic understanding, and expressive language skills than toddlers with TD matched on mental age.  This study represents one of the first studies examining whether the CSBS is appropriate for comparing groups matched on mental rather than chronological age.  Further, these preliminary results suggest that nonverbal mental age is related to ASD symptoms, such that those toddlers with higher nonverbal skills showed milder symptoms.  Finally, it is hypothesized that early repetitive behaviors will be related to these core symptoms of ASD and data analyses to address this question is ongoing.