  Psychological behaviorism’s historical roots consist, in part, in the classical associationism of the British Empiricists, foremost John Locke (1632–1704) and David Hume (1711–76). According to classical associationism, intelligent behavior is the product of associative learning. As a result of associations or pairings between perceptual experiences or stimulations on the one hand, and ideas or thoughts on the other, persons and animals acquire knowledge of their environment and how to act. Associations enable creatures to discover the causal structure of the world. Association is most helpfully viewed as the acquisition of knowledge about relations between events. Intelligence in behavior is a mark of such knowledge.