Investigates the prediction that the usual superiority of pictures over words for repetitions of the same items would disappear for items that were different instances of repeated categories. (Author/RK)

Pigeons learned discrimination rapidly and responded differentially to pictures seen for the first time. The essential feature of a natural discrimination--which is the ability to cope with natural ranges of variation--was approached and earlier experimental results were extended using other classes of stimuli. (Author/RK)

The purpose of this study was to empirically test a set of predictions implied by the Model of Conceptual Learning and Development using the concept of cutting tool. Four subtests were developed to assess a subject's ability to perform at each of four successive levels of concept attainment (concrete, identity, classificatory and formal). In…