Studies 12- to 24-month-olds in a series of videotaped tasks assessing single object manipulation, relational play, pretend play, distractibility and persistence. Develops eight relatively subtle measures of three aspects of individual differences in infant behavior: developmental level, attention span, and exploratory diversity. (Author/NH)

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)