Discourse skills of boys with fragile X syndrome in comparison to boys with Down syndrome.

Purpose: This study compared the conversational discourse skills of boys who have fragile X syndrome with and without autism spectrum disorder (ASD) with those of boys with Down syndrome and boys who are typically developing.

Method: Participants were boys who have fragile X syndrome with (n = 26) and without (n = 28) ASD, boys with Down syndrome (n = 29), and boys who are typically developing (n = 22). Turns during an examiner-child interaction consisting of structured and semistructured activities were coded for the boys' ability to maintain a topic of conversation and the frequency of perseveration.