Abstract
Minimally verbal children constitute a portion of the autism spectrum. The paucity of proper measurement tools that sensitively and accurately assess behaviors has been one limiting factor in the improved knowledge of these children. Short of creating and validating a new measurement tool for this subpopulation, this study took an alternative and more immediate approach: conduct a secondary data analysis and examine an existing social communication measure, the Early Social Communication Scales (ESCS), with item response theory. The final sample consisted of 453 minimally verbal children culled from four different completed studies. The IRT models analyzed the frequency of social communication gestures from the ESCS and returned an objective difficulty hierarchy regarding initiations of joint attention and behavior regulation gestures. The best-fitting and final model was a zero-inflated negative binomial model (ZINBM), which determined that joint attention gestures were, on average, more difficult than behavior regulation gestures. Joint attentional shows and gives were essentially absent in the children's repertoire, and behavior regulation reaches were the easiest gestures for this sample. The ZINBM separately modeled children with some gestures and children who did not present with any gestures and determined that behavior regulation reaches and gives were likely the first gestures a child will eventually exhibit among children with no gestures. Methodological contributions and potential future applications of IRT are discussed.