Non-Directed Gesture Use In Infant Siblings at Risk for ASD

Background: Gestures in infancy play a fundamental role in prelinguistic communication and the development of language and play. Early gesture use predicts language outcomes in both typical and atypical development. Our previous work showed that infants who went on to have a diagnosis of ASD showed delayed gesture development by 12-months. Conventionally, three elements, taken together, define a gesture: 1) an action produced with hands, arms, fingers, body or face, that is 2) directed to a person, and 3) serves a communicative function (e.g., requesting objects). However, gesture use in infants at risk for ASD may not contain all components; for example, it is possible that they produce gestures (e.g., point) but do not direct them to a person. 

Objectives: This study compared directed and non-directed gesture use in 15-month-old infant siblings at risk for ASD (AR-ASD) and infants at low risk (LR) for developmental concerns.

Methods: Sixteen, 15-month old, infant siblings were recruited from a longitudinal study of infants with an older sibling with ASD (AR-ASD, n = 8; LR, n = 8). The AR-ASD group was selected from the longitudinal study on the basis of having elevated scores on our Autism Observation Scale for Infants (AOSI: Bryson et al., 2008). LR infants were selected on the basis of having passed a parent-reported evaluation of prelinguistic development (CSBS-DP ITC; Wetherby & Prizant, 2002) prior to age 15 months. Average scores on the Mullen Scales of Early Learning at 12 months confirmed absence of developmental delays in the LR group. Infants were videotaped during a standardized administration of the CSBS-DP (15-20 minutes). Gestures were coded for directedness. Directedness included; a) gave or moved an object toward a person, b) touched a person, d) coordinated a gesture with eye gaze or vocalization, or e) produced a gesture in response to a previous statement or action. Directed gestures were also coded by type (e.g., deictic) and function (e.g., joint attention) although only data on directedness are reported here. Directed (d+) and non-directed (d-) gesture rates (per minute) were calculated for each infant. 

Results: Two independent samples t-tests were conducted to evaluate the hypothesis that infants at risk for ASD have a lower rate of d+ gestures and a higher rate of d- gestures than LR infants. AR-ASD infants had a significantly lower rate of d+ gestures, t(14) = 2.86,  p<.05, d = 1.43, and a higher rate of d- gestures than LR infants, t(14) = -2.84,  p<.05, d = -1.42. 

Conclusions: Compared to infants without developmental concerns, 15-month old infants at risk for ASD use directed gestures at a lower rate and more often produce gestures that are not directed to others. These results have important implications for early intervention. Intervention goals may need to include targeting directedness (e.g., adding eye gaze or vocalization to non-directed) to gestures produced in order to increase their saliency by making them more communicative. This may then impact caregivers’ responsiveness to these less clear communicative attempts, thereby increasing the likelihood of their recurrence.