Recent reports using a classical behavior genetic research design in which twin data are combined with a measured characteristic of their shared family environment have made striking claims about estimating environmental influences on behavior with genetic effects controlled. Such claims are overstated for two related reasons. First, when a…

The relation between maternal presence and infant's vocalization depended upon the infant's state: when the infant was in the active awake state, he vocalized less in the presence of the mother than when alone, thus indicating that the majority of early vocalizations are associated with a non-social situation. (Authors/RY)

Purpose of this paper is to discuss some of the environmental and behavioral factors in children's day-to-day lives that are associated with hyperactivity and to examine its stability over time. (Authors)