Current research on conditioning and learning reflects three themes: a methodological behavioral theme that focuses on how certain experiences lead to changes in behavior, a cognitive theme that focuses on how experiences are represented in memory, and an evolutionary/adaptive behavior theme that focuses on the various kinds of learning as adaptive specializations that evolved through the mechanism of natural selection. These themes are interwoven to present an integrated and coherent account of our current state of knowledge in the area. The evolutionary/adaptive behavior theme is the central theme within which the cognitive and behavioral themes are developed here.