Signs of Autism Spectrum Disorder Appear as Early as Infancy

mother holding baby
mother holding baby
A team of investigators examined repetitive behavior exhibited among children later diagnosed with autism spectrum disorder.

Infants who later developed autism spectrum disorder (ASD) were found to observe objects more closely and more frequently than infants who did not develop ASD, according to a recent study. This behavior was found to manifest by as early as 9 months of age.

Repetitive behavior is a core diagnostic component for ASD. The researchers in the study published in the Journal of Abnormal Psychology investigated whether this type of behavior manifests before a child’s first birthday.

The prospective longitudinal study involved infant siblings of children with ASD or without ASD. The infants were evaluated at 9, 12, 15, 18, 24, and 36 months of age. Of the 185 enrolled infants, 156 completed the final outcome assessment at 36 months. The final analyzed sample included 147 infants. Trained raters examined the infants for prolonged object exploration and social responsiveness.

The researchers found infants in the ASD group exhibited 139% more unusual visual inspection of objects compared with infants in the low-risk, non-ASD group. Differences in both spinning and rotating behavior in the ASD group compared with the low-risk, non-ASD group appeared to be related to risk for ASD rather than differences specific to outcome.

The researchers also found an association between unusual visual inspection and social engagement. “Unusual visual inspection at 9 months of age predicted social engagement at 12 months, B=0.21 SE=0.08, p=.01, 95% CI [0.05, 0.38], with higher levels of unusual visual inspection predicting lower levels of social engagement (on the original scale),” the researchers state.

Other types of relevant repetitive behaviors were not evaluated, representing a possible limitation of this study. The researchers also report the possibility of missing data and note the study’s small sample size.

“Overall, we found that unusual visual inspection of objects is present in ASD earlier than previously thought and is, to our knowledge, one of the earliest behavioral predictors of ASD outcome yet documented,” the researchers report. “Our findings suggest that close monitoring of unusual visual inspection of objects by 9 months of age may be an important aspect of early detection efforts and may be valuable to integrate into early screening and diagnostic tools.”


Miller M, Sun S, Iosif A-M, et al. Repetitive behavior with objects in infants developing autism predicts diagnosis and later social behavior as early as 9 months. J Abnorm Psychol. 2021;130(6):665-675. doi:10.1037/abn0000692