Date of Award

Fall 2019

Document Type

Open Access Dissertation



First Advisor

Jane E. Roberts


Background: Social Anxiety is diagnosed in approximately 10% of neurotypical children. If left untreated, negative outcomes are highly prevalent later in life. Thus, understanding the earliest features of social anxiety can help to mitigate detrimental outcomes. Fragile X Syndrome, which has a high prevalence of social anxiety, is a genetic syndrome which creates a unique opportunity to study the earliest predictors of social anxiety before formal diagnosis. Fragile X Syndrome presents with intellectual disability and an increased prevalence of maladaptive behaviors. The current study utilized a bio-behavioral approach to study the earliest marker of social anxiety in 12- month-old infants with fragile X syndrome.

Method: Participants included 32 infants with FXS (M (SD): 12.41 (1.49)) and 41 low risk controls ((M (SD): 12.41 (0.60)). Parent reported social behavioral inhibition was recorded from the Infant Behavior Questionnaire (IBQ-R), which reflects infants’ responses in a social context. Observed social behavioral inhibition and physiology was measured during the Stranger Task of the Laboratory Temperament Assessment Battery (Lab-TAB). This task is designed to elicit social behavioral inhibition in infants and young children. Group differences were assessed using independent sample t-tests. Differences in physiological response was tested using a repeated measure mixed effect linear model with condition, group, Mullen ELC, and group by condition interaction included as predictors.

Results: . Parent-reported social behavioral inhibition was not significantly different between groups. Infants with FXS demonstrated less social behavioral inhibition but increased gaze vigilance towards the stranger in comparison to LRCs. Physiological response was blunted in infants with FXS, but not LRC peers.

Conclusions: Findings suggest that infants with FXS are showing both physiological and attentional markers of social anxiety at 12 months old. However, no differences were observed in either parent-reported or observed social behavioral inhibition. Results highlight the importance of a multi-method approach to understanding the complex phenotype of social anxiety in FXS. Future studies should examine longitudinal trajectories of infants with FXS to include social anxiety diagnosis outcome data.