For many decades, tool use has been viewed primarily as a cognitive achievement, an ability that separates not only adults and older children from infants, but humans from virtually all other species. According to this standard account, tool use and associated means-ends behaviors are dependent on symbolic or representational thinking. Organisms…

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)