Does Having a Sibling Affect Autistic People's Empathy?

This study examined whether autistic people with siblings score higher on measures of empathy than those without siblings. Cohorts of autistic children (n = 939; mean age = 7.35 years (SD = 2.15)) and autistic adults (n = 736; mean age = 37 years (SD = 12.39)) from the Cambridge Autism Research Database (CARD) were each divided into two groups: with or without siblings. Empathy was measured using the children version of the Empathy Quotient (EQ) (parent-report) for children. For adults, the EQ (self-report version) and the Reading the Mind in the Eyes Test (RMET) were used. Contrary to the hypothesis, autistic children without siblings scored higher on EQ than those with siblings (t_(283.70) = 4.20, p < .001; d = 0.50). In adults, there was no difference between autistic adults with and without siblings on both measures, but there was an interaction effect between sex and group on the RMET (f₍₁₇₃₂₎ = 4.10, p = 0.04): whilst autistic males without siblings on average scored lower than females, autistic males with siblings on average performed similarly to females. Future research should investigate the possible effect of siblings on autistic males' empathy performance in a larger cohort of autistic individuals. Children's empathic abilities may be underestimated by their parents when they have siblings due to a contrast effect.