Species-specific defense reactions and avoidance learning.

The prevailing theories of avoidance learning and the procedures that are usually used to study it seem to be totally out of touch with what is known about how animals defend themselves in nature. This paper suggests some alternative concepts, starting with the assumption that animals have innate species-specific defense reactions (SSDRs) such as fleeing, freezing, and fighting. It is proposed that if a particular avoidance response is rapidly acquired, then that response must necessarily be an SSDR. The learning mechanism in this case appears to be suppression of nonavoidance behavior by the avoidance contingency. The traditional approaches to avoidance learning appear to be slightly more valid in the case of responses that are slowly acquired, although in this case, too, the SSDR concept is relevant, and reinforcement appears to be based on the production of a safety signal rather than the termination of an aversive conditioned stimulus. Avoidance learning as we know it in the laboratory has frequently been used to explain how animals survive in the wild. The purpose of this paper is to turn this inferential process around and use the limited knowledge of natural defensive behavior to help account for some of the anomalies that have been found in laboratory studies of avoidance learning. Let us begin by recalling a little fable. It is a very familiar fable. It was already part of our lore when Hull gave his version of it in 1929, and the story has been told again many times since then. It goes something like this: Once upon a time there was a little animal who ran around in the forest. One day