Describes and discusses the rule-assessment approach, a new research strategy for studying developmental sequences in children's acquisition of knowledge. Four experiments were conducted to illustrate the utility of this approach across a variety of concepts and a wide range of ages (three-year-olds to college students). (Author/CM)

Reports a series of studies conducted to investigate possible differences in the exploratory manipulation and play behavior of human infants 7-1/2- 11-1/2 months of age as a function of the attributes of the stimulus, the familiarity of the subject with the stimuli, the age and sex of the infants, and individual differences. (Author/CS)