Publication Date



Open access

Degree Type


Degree Name

Doctor of Philosophy (PHD)


Psychology (Arts and Sciences)

Date of Defense


First Committee Member

Marygrace Yale-Kaiser - Committee Member

Second Committee Member

Kristin Lindahl - Committee Member

Third Committee Member

Michael Alessandri - Committee Member

Fourth Committee Member

Daniel Messinger - Mentor

Fifth Committee Member

Monica Dowling - Outside Committee Member


Siblings of children with autism (ASD-sibs) often exhibit deficits in social reciprocity and cognitive deficits similar to those of their affected siblings. The purpose of this study was to examine the associations between degree of autistic symptomatology and degree of cognitive functioning in sibling pairs seen as part of a longitudinal ASD-focused sibling study. Both cognitive functioning and autistic symptomatology were assessed using continuous measures in sibling pairs. Three sets of bivariate correlations were conducted to examine the relationships between autistic symptomatology and cognitive ability. One ANCOVA and 6 ANOVAS were also conducted to identify possible group differences between younger siblings of children with diagnoses of ASDs (ASD-sibs) and younger siblings of children without diagnoses of ASDs (COMP-sibs). When associations were examined in the entire sample, all correlations examined were significant, p <.05. However, when examined by group, no associations between younger and older siblings were significant. Negative correlations were found between ASD symptomatology and cognitive functioning within the younger sibling, and between ASD symptomatology and cognitive functioning within the older sibling. Thus, within the ASD group, level of autistic symptomatology was negatively associated with level of cognitive functioning with individuals. Results indicate that intellectual disability (i.e., impaired cognitive functioning) runs in concert with symptomatology among children with ASDs and among their younger siblings. Additionally, by three years of age, ASD-sibs were receiving lower scores than COMP-siblings in the areas of receptive language, expressive language, and in visual reception. Clinically, the identification of specific limitations in ASD-sibs has important implications for intervention programs which could help to prevent or ameliorate poor outcomes.


Sibling; Autism