Perseveration in the connected speech of boys with Fragile X syndrome with and without autism spectrum disorder.

Verbal perseveration is a frequently reported language characteristic of males with Fragile X syndrome and may be a defining feature or hallmark of the syndrome. We compared the verbal perseveration of boys with Fragile X syndrome with (n  =  29) and without (n  =  30) autism spectrum disorder, boys with Down syndrome (n  =  27), and typically developing boys (n  =  25) at similar nonverbal mental ages. During a social interaction, boys with both Fragile X syndrome and autism spectrum disorder produced significantly more topic perseveration than all other groups.