Calorie Learning: Background

The discovery of flavor-calorie learning (in rats) was no surprise. It was another example of flavor-consequence learning, which was well established. In the 1950s, John Garcia had found that if you make a rat sick after exposing it to a new flavor, it will avoid that flavor. Flavor-consequence learning belongs to the larger category of Pavlovian learning (also called classical conditioning), the sort of learning where an animal learns that an unimportant event (such as a bell) predicts an important event (such as food). Pavlovian learning belongs to the larger category of associative learning, which also includes action-event learning, such as a rat learning that bar presses produce food pellets. The action is pressing the bar; the event is getting a food pellet.

My Ph.D. was in the field of animal learning. Almost all animal learning research is about associative learning. When I taught introductory psychology, however, I found it hard to take advantage of my expertise because most of the research had little real-world relevance. The big exception was Shepard Siegel’s work on drug tolerance and craving. Tolerance and craving are due to Pavlovian learning, Siegel argued. Flavor-calorie learning, happening at every meal, might have been another exception had anything interesting been known about it — but nothing was.

The usual terminology is to say that in a Pavlovian-learning experiment, the animal learns to associate the CS (conditioned stimulus, such as a bell) with the US (unconditioned stimulus, such as food). In flavor-calorie learning experiments, the flavor source is the CS, the calorie source the US.