Maternal structure and autonomy support in conversations about the past: contributions to children's autobiographical memory

The authors examined the contributions of maternal structure and autonomy support to children's collaborative and independent reminiscing. Fifty mother-child dyads discussed past experiences when the children were 40 and 65 months old. Children also discussed past events with an experimenter at each age. Maternal structure and autonomy support appeared as 2 distinct and separable components of mothers' reminiscing style and acted in an additive fashion to predict children's memory. Children whose mothers demonstrated both high structure and high autonomy support provided the greatest memory in these conversations, whereas children whose mothers were low on both dimensions provided minimal memory. The authors discuss the implications of these effects for children's autobiographical memory development.     

Sources of exposure to smoking and drinking friends among adolescents: a behavioral-genetic evaluation

Substance-using friends expose adolescents to models of, and opportunities for, substance use that may lead to its initiation or reinforce existing use. Using genetically informative data from the National Longitudinal Study of Adolescent Health (P. S. Bearman, J. Jones, & J. R. Udry, 1998), the authors examined whether adolescents' exposure to friends' tobacco smoking and alcohol drinking was better explained by family-social or genetic influences. To conduct analyses, the authors constructed substance use exposure scores for adolescent siblings from the responses of siblings' nominated friends to self-reported smoking and drinking items. Using behavioral-genetic analyses of these substance use exposure scores, the authors estimated that 64% of the variance in adolescents' exposure to friends who smoke and drink could be explained by genetic influences, whereas shared environmental influences were zero. These results provide evidence of active, evocative, or both types of gene-environment correlations. Genetic factors can influence the formation of friendships with substance-using peers, thereby contributing to adolescents' exposure to substance use behaviors.     

The use of numerical and graphical statistical methods in the analysis of data on learning to see complex random-dot stereograms

Several numerical and graphical statistical methods are illustrated in an analysis of data from an experiment that investigated a hypothesis of Julesz that giving a person a priori information about the structure of a complex random-dot stereogram reduces the time needed to perceive it when it is viewed. The data are divided into two groups, one consisting of those observers who received no cue or verbal cues (NV) and the other consisting of those who received verbal-visual cues (VV). A quantile-quantile plot shows that the NV times (mean = 7.6) are longer than the VV times (mean =5.6). By using probability plots, it is shown that the perception times have an exponential probability distribution. A hypothesis test based upon this distribution is used to show that the difference between the NV and VV times has significance slightly below 0.05.