More boys than girls have ASD at a ratio of 4:1 (Baio et al., 2018). In general, boys tend to demonstrate more ritualistic and repetitive behaviors (RRBs) than girls (Szatmari et al., 2012) though a gender bias may lead to under diagnosis of girls. Therefore, a female phenotype should be differentiated to improve diagnostic accuracy.

This study seeks to describe and compare RRB profiles and frequencies in two age cohorts of girls and boys with ASD as measured by the Repetitive Behavior Scale-Revised (RBS-R) and the Childhood Routines Inventory (CRI).

214 children with ASD (42 girls; 172 boys) between 16 months and 10 years old (mean = 46.1 months) were included from an ASD clinical research database Two age cohorts were used (1-3 years; 4-10 years) to compare RRBs using parent reports.

Girls younger than 3 had more repetitive (t = -1.66; p = .03), ritualistic (t = -.12; p = .004), and sameness behaviors (t = -1.9; p = .002). Older girls had more stereotyped behaviors than boys (t = -2.2; p = .001) and more ritualistic behaviors in general. Younger girls (n = 23) had more stereotyped (62.7%), restricted interests (58%), sameness (41%), compulsive (46%), ritualistic (36%), and self-injurious behavior (27%). Boys displayed RRBs and stereotypical behaviors. Girls demonstrate more repetitive behaviors than boys. RRB patterns and profiles will be discussed comparatively. These findings contribute the understanding of the female ASD phenotype.