Habituation is important, but it tells the organism about only a single stimu-lus—is the stimulus novel and so worth exploring, or familiar and therefore safe to ignore? Other forms of learning provide more information and, in particular, provide the organism with information about the relationships among events in the world.
Relationships come in many varieties. One event might cause another; an action might prevent some outcome; a certain circumstance might magnify an experience; and so on. Overall, though, relationships can usually be understood in terms of associations: Your dog learns to associate the sound of your foot-steps with the possibility of a treat; you have learned to associate thunder with light-ning; the farmer’s cows learn to associate a certain time of day with milking. Th importance of these associations was, as we’ve seen, highlighted by the empiricistphilosophers, but the experimental study of these associations did not begin until theend of the late 1800s, when the work of the Russian physiologist Ivan PetrovichPavlov (1849–1936) made a major contribution (Figure 7.2).