Whereas some four year olds could draw a person with five fingers on each hand and a full set of facial features, others could barely hold a pencil. Some sat quietly in a small group, intently listening to and understanding a story, while others wiggled, fidgeted, and couldn't focus their attention. In those days, before the explosion of…

Examines the interplay between genes and environment and argues that the development of much individual variation can be explained in terms of relatively simple forms of underlying regulation. Looks at "sensitive periods," during which variation is produced by experience received at a particular age. Includes a discussion of the…

It is concluded that equality of endowment is a myth dreamed up for ideological and political reasons. Educational policies must not be dictated by such fictions which fail to take into account biological reality. More quantitative studies are required to make equality of opportunity a concrete and realistic ideal. (EH)

Although it is difficult to ascertain precisely the time at which the study of individual differences became recognized as a specialty within the psychological sciences, there appears to be much agreement among historians that its development was fostered primarily within the United States during the late 19th century. This paper examines the…

The language development of monozygotic twins, same-sex dizygotic twins, siblings of monozygotic twins, and siblings of dizygotic twins, ages 3-17, was studied to estimate how much of the individual variation in children's language skills results from genetic factors and how much from environmental experience. (BRT)

Areas of agreement and disagreement concerning intellectual developmental and the problems of mental retardation espoused by the author and by Uzgiris are discussed in this paper. The importance of environmental factors, along with the genetic and/or constitutional nature of the organism on which these environmental events impinge, is seen as…