Comparing gesture frequency between autistic and neurotypical individuals: A systematic review and meta-analysis.

While diagnostic assessments for autism routinely screen for reduced frequency of gestures, evidence supporting reduced gesture production in autism is inconsistent. This systematic review and meta-analysis aimed to clarify differences in frequency of gestures between autistic and neurotypical individuals. Included studies compared frequency of gestures between autistic and neurotypical individuals. Database searches (APA PsycInfo, ERIC, MEDLINE, ProQuest Dissertations and Theses Global) and a call for unpublished data on the International Society for Gesture Studies listserv identified research from January 1994 to March 2023. Study quality was assessed using the Joanna Briggs Institute Critical Appraisal Checklist for Quasi-Experimental Designs. Quantitative synthesis involved a narrative review of all findings and meta-analysis of articles allowing effect size calculations, stratified by the type of gesture. Thirty-one articles comparing frequency of gestures between 701 autistic and 860 neurotypical individuals were included in the narrative review, 25 of which were also included in the meta-analysis. Compared to neurotypical individuals, meta-analyses found that autistic individuals produced significantly less total, deictic, and emblematic gestures. While the number of iconic gestures appeared comparable between groups, studies investigating iconic gestures exhibited an almost equal trend of both positive and negative effect sizes, which were mostly nonsignificant. The way gesture production was measured, age, observer familiarity, and task structure (but not overall study quality) moderated the effect size, albeit inconsistently across the types of gestures. Findings have implications relating to profiling gesture use in diagnostic assessments for autism and highlight gaps in our understanding of differences in gesture production in autism. (PsycInfo Database Record (c) 2023 APA, all rights reserved).