Research on sources of individual difference in parental Infant-Directed Speech (IDS) is limited and there is a particular lack of research on fathers' compared to mothers' speech. This study examined the predictive relations between infant characteristics and variability in paternal lexical diversity (LD) in dyadic free play with two-year-olds (M…

The newest edition of the "Diagnostic and Statistical Manual of Mental Disorders" (5th ed., DSM-5) introduced substantial changes to the diagnostic criteria for autism spectrum disorder, including new severity level ratings for social communication and restricted and repetitive behavior domains. The purpose of this study was to evaluate…

Infants judged to be at risk for subnormal intellectual growth were randomly assigned to experimental and control groups which varied as to educational curriculum activities. Two types of evidence, group differences and parent-child IQ correlations, demonstrate the importance of early environments in intellectual development. (Author/RD)