ABSTRACT
One of the fundamental questions of animal cognitive psychology concerns the nature and processes determining the effective stimulus in any discrimination. In his 40 years at Berkeley, this question, in one form or another, has been the theoretical and experimental foci for Donald Riley, his many students, and collaborators. These experiments have examined a broad range of topics, with inquiries into transposition in both children and rats, conditioning in the octopus, selective and divided attention in pigeons, echolocation in rats, and verbal learning and memory in humans (Postman & Riley, 1959; Riley, Goggin, & Wright, 1963; Riley & Leith, 1976; Riley & McKee, 1963; Riley & Rosenzweig, 1957; Warren, Riley, & Scheier, 1974).
