The Presence of Restricted and Repetitive Behaviors in Infants and Toddlers with Typical Development

Background: Early diagnosis of autism spectrum disorders (ASD) has become increasingly common, due in part to research highlighting the importance of early identification and intervention. If ‘red flags’ for ASD are to be accurately identified, researchers and clinicians must have a good understanding of the range of behavior that can be expected in very young children with typical development.  Yet to date, relatively little is known about the prevalence of restricted and repetitive behaviors (RRBs) and other ‘unusual’ behaviors in very young children with typical development (TD), despite the fact that these behaviors constitute a core component of the ASD phenotype.

Objectives: The aim of the present study is to learn more about the presence of repetitive and other ‘unusual’ behaviors in very young typically developing children.

Methods: Data were analyzed for 110 TD children (7-24 months old) who were evaluated as part of the development of the Autism Diagnostic Observation Schedule (ADOS) Toddler Module. Analyses included 4 items that are part of the RRB section of the ADOS Toddler Module (hand/finger mannerisms, other complex mannerisms, unusual sensory interests, unusually repetitive interests/stereotyped behaviors); and 5 items in the Communication section that involve unusual and/or repetitive forms of communication (echolalia, stereotyped speech, frequency of undirected vocalizations, use of other’s body to communicate, unusual intonation).

Results: Undirected vocalizations were significantly more common in children under 18 months compared to children over 18 months, χ² = 18.8, p < .001, as were hand/finger mannerisms, χ² = 8.8, p < .01. There were no gender differences for any of the behaviors. Nearly all the behaviors analyzed were present in a substantial minority (i.e., between one-third and half) of the participants. Only two behaviors, unusual sensory interests and other complex mannerisms, were present in less than 25% of children. Although most individual behaviors were relatively common, few children received high total scores across these items, because each behavior they exhibited was relatively infrequent and/or because they tended to exhibit only one or two behaviors.

Conclusions:  The present findings are consistent with previous studies of preschool-age children and indicate that so-called ‘unusual behaviors’ are far from rare in  typically developing infants and toddlers.   The findings on age differences suggest that some of these behaviors might become less common with age. Although most of the behaviors examined were not uncommon, it was rare for children to exhibit several behaviors and/or to display a given behavior frequently. Thus, although the presence of a single repetitive behavior should not be considered a ‘red flag’ for ASD, the existence of several or frequent ‘unusual’ behaviors should be. That being said, the fact that a small subsample of TD children had high total scores suggests that even with a conservative approach to diagnosis, there is still the risk for false positives, particularly if clinicians are swayed by the presence of ‘unusual’ behaviors. These findings therefore highlight the importance of clinical expertise in the complexities of both typical development and the very early ASD phenotype across several domains of behavior.