This analysis examines the dynamic reciprocal relationship between delinquent peer associations and delinquent behavior. It tests the hypothesis, derived from learning and interactional theories, that delinquent peers and delinquent behavior are reciprocally related—delinquent peer associations foster future delinquency, and delinquency increases the likelihood of associating with delinquent peers. It also tests the competing hypothesis, derived from control theories, that delinquent peers do not cause delinquency, but instead, the relationship is (1) spurious due to individual criminal propensity, (2) a result of the effects of delinquent behavior on future associations with delinquent peers, or (3) an artifact of problems of measuring delinquent peers. To test these propositions, we use data from the National Youth Survey and estimate a cross‐lagged panel model that corrects for measurement error in indicators of delinquent peers and delinquent behavior. The model species a covariance structure model for ordinal measures. Parameters are estimated by (1) estimating a threshold model relating ordinal measures to continuous latent variables; (2) estimating a matrix of polychoric correlations relating observed variables, and (3) using an asymptotic distribution‐free estimator to estimate structural parameters. The results suggest that delinquent peer associations and delinquent behavior are reciprocally related, but the effect of delinquency on peer associations is larger than that of peer associations on delinquency.

Boys with FXS and DS have distinctive language profiles. Although both groups demonstrated syntactic delays, boys with DS showed greater delays.

No abstract

In this study, the authors compared the phonological accuracy and patterns of sound change of boys with fragile X syndrome, boys with Down syndrome, and typically developing mental-age-matched boys. Participants were 50 boys with fragile X syndrome, ages 3 to 14 years; 32 boys with Down syndrome, ages 4 to 13 years; and 33 typically developing boys, ages 2 to 6 years, who were matched for nonverbal mental age to both the boys with fragile X syndrome and the boys with Down syndrome. All participants were administered a standardized articulation test, and their sound accuracy, phonological process, and proportion of whole-word proximity scores were analyzed. Although boys with fragile X syndrome were delayed in their speech development, they did not differ from the typically developing, mental-age-matched boys in the percentage of correct early-, middle-, and late-developing consonants; phonological processes; or whole-word proximity scores. Furthermore, boys with fragile X syndrome had fewer errors on early-, middle-, and late-developing consonants; fewer syllable structure processes; and higher whole-word proximity scores than did boys with Down syndrome. Boys with Down syndrome also were delayed in their speech development, yet their phonological inventories, occurrences of phonological processes, and proportion of whole-word proximity scores indicated greater delays in their phonological development than the younger, typically developing boys. These results suggest that males with fragile X syndrome display phonological characteristics in isolated words similar to younger, typically developing children, whereas males with Down syndrome show greater delays as well as some developmental differences compared with both the males with fragile X syndrome and typically developing males.

Boys with fragile X syndrome with (n = 49) and without (n = 33) characteristics of autism spectrum disorder, boys with Down syndrome (39), and typically developing boys (n = 41) were compared on standardized measures of receptive vocabulary, expressive vocabulary, and speech administered annually over 4 years. Three major findings emerged. Boys with fragile X without autism spectrum disorder did not differ from the younger typically developing boys in receptive and expressive vocabulary and speech production when compared at similar levels of nonverbal cognitive skills. Boys with fragile X without autism spectrum disorder and typically developing boys had higher receptive vocabulary and speech production than did boys with Down syndrome. There were mixed patterns of results for the boys with fragile X and characteristics of autism spectrum disorder.