Joint attention performance in preschool-aged boys with autism or fragile X syndrome.

Early development marks a period of rapid learning facilitated by children's natural curiosity about the people around them. In children with typical development, these early social attentional preferences set the foundation for learning about and from the surrounding world of people. Much of this learning happens using joint attention, the ability to coordinate attention between people and objects of mutual interest. It is well documented that decreased gaze use is commonly observed in individuals with autism and individuals with fragile X syndrome (FXS). Despite the growing body of research comparing phenotypic similarities between individuals with autism and individuals with FXS, no studies have directly compared joint attention performance between these groups. In the present study, we considered the similarities and differences in joint attention between preschool-aged boys with autism or FXS, and the relation between joint attention, language, and other phenotypic characteristics known to differ between boys with autism and boys with FXS. Although joint attention appeared similar, between-group differences emerged when controlling for the influence of age, non-verbal IQ, and autism symptom severity. Differences were also observed when considering how joint attention performance related to other aspects of the phenotype. For example, strong positive associations were observed between joint attention and language performance in boys with autism but not boys with FXS, even after controlling for non-verbal IQ. In contrast, the negative association between joint attention and anxiety symptom severity was significant and stronger in boys with FXS than in autism. These data offer preliminary insights into the similarities and differences between the autism and FXS phenotypes.