A Comparison of Reaching Coordination and Arm Postures Between Infant Siblings of Children with Autism and Typically Developing Infants at 3 and 6 Months of Age

Background: Infants begin to reach for objects between 3 and 5 months of age. In the months before reaching emerges, infants perform a variety of early arm movements that change in a predictable fashion closer to the week of reach onset. The developmental trajectory of transition to reaching is such that infants progress from side to midline postures, closed-handed to open-handed reaches, and accidental contacts to consistent reaching (Savelsbergh and van der Kamp, 1994 ). Infants who later develop autism spectrum disorders (ASD) are known to have fine-motor delays as early as 6 months. (Landa and Garrett-Mayer, 2006).

Objectives: The objective of this study was to further describe the reaching abilities of infant siblings of children with ASD (AU sibs), a group at higher risk for developing ASD as compared to typically developing (TD) infants at 3 and 6 months of age. We hypothesized that AU sibs would show differences in frequency and quality of reaching as well as duration of specific arm postures as compared to TD infants.
Methods: 15 AU sibs and 15 TD control infants were tested between 3-4.5 months and 6-7.5 months of age. At 3 months, infants laid supine as they attempted to contact a midline toy at arm’s length. At 6 months, infants were sitting with minimal support as a toy was presented in the midline and to both sides at arm’s length. Video data were later coded for frequency of toy contacts and open-ventral vs. closed-dorsal reaches. We also coded the percent duration of time spent in the following arm postures: at side, on chest, in mouth, in front, and at knees. A single coder maintained intra-rater and inter-rater reliability of above 98%.

Results: At 3 months, AU sibs had significantly fewer toy contacts (p=0.02), fewer open-handed reaches (p=0.009) as compared to Controls. Analysis of infant arm postures revealed that the majority of the AU sibs placed their arms near the chest or in the front regions without consistent reaching suggesting that AU sibs were either non reachers or emerging reachers. In contrast, the Controls had more experience reaching for objects and the majority of the Controls were consistent reachers. At 6 months, there were no group differences in reaching frequency or quality. However, AU sibs had significantly fewer reach and grasp movements as compared to Controls indicating that  AU sibs frequently dropped the toy out of their hand after reaching for it.

Conclusions: The transition to reaching allows infants to independently explore and manipulate their environment. Specifically, object interactions create contexts for communication with caregivers, for learning of object properties, and facilitate future social and cognitive development. Furthermore, fine-motor skills such as reaching and grasping are a foundation for future gestural communication. Thus, our results on delays in reaching and grasping found in AU sibs may be early markers of future non-verbal and verbal communication delays. Overall, these results highlight the importance of incorporating reliable reaching and grasping measures within any early identification tool for ASD.