Abstract
Previous studies have reported a specific behavioral phenotype, or a distinct profile of behavioral outcomes, associated with Down syndrome. Until recently, however, there has been little attention given to how this behavioral profile emerges and develops over time. It is argued here that some aspects of the Down syndrome behavioral phenotype are already emerging in infants and toddlers, including emerging relative strengths in some aspects of visual processing, receptive language and nonverbal social functioning, and relative weaknesses in gross motor skills and expressive language skills. Research on the early developmental trajectory associated with Down syndrome (and other genetic disorders) is important because it can help researchers and practitioners formulate interventions that are time-sensitive, and that prevent or offset potential future negative outcomes. This article reviews evidence for the emerging Down syndrome behavioral phenotype in infants, toddlers, and preschoolers. This is followed by a discussion of intervention approaches that specifically target this developing profile, with a focus on language, preliteracy skills, and personality motivation.