Date of Award

Fall 2025

Document Type

Open Access Thesis

Department

Psychology

First Advisor

Jessica Bradshaw

Abstract

With the acquisition of early motor milestones, infants gain an enhanced ability to interact with their social and physical environments. Advanced motor skills provide richer input from objects and caregivers that supports other developing systems, including language and cognition (Iverson, 2021). Current research suggests that differences in postural control may be among the earliest behavioral markers of ASD (Bradshaw et al., 2023; Flanagan et al., 2012). A recognizable motor milestone, like unsupported sitting, may serve as a useful predictor of social communication skills, with delays in its onset indicating a greater need for early intervention and developmental monitoring. This study aimed to 1) compare the unsupported sitting ability of 6-month-old infants who were later diagnosed with or without ASD and 2) examine whether the association between 6-month sitting ability and social communication skills at 24 months differs between diagnostic groups. Data were collected longitudinally from 101 full-term infants who were at an elevated (n = 46) or a low likelihood (n = 55) for ASD. Results found that unsupported sitting was comparable between diagnostic groups, however, infants with ASD who achieved unsupported sitting by 6 months went on to exhibit superior social communication skills at 24 months, compared to ASD-supported sitters. This suggests that delays in motor skill attainment can have cascading effects on other developing systems (i.e., social communication), particularly for infants with ASD who are already vulnerable to such delays. Taken together, current early interventions may be overlooking the important role of motor skill development in supporting social and communication outcomes.

Rights

© 2025, Emma Platt

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