Conditioned and unconditioned defensive burying in the rat

Abstract

When rats first encountered a mouse-trap or a flashbulb in a chamber to which they had been habituated, they buried it with bedding material from the floor of the chamber, whereas rats previously habituated to the trap or the flashbulb did not. Conversely, rats did not bury a stationary, wire-wrapped wooden prod or a length of polyethylene tubing, even on first encounter. However, almost every rat struck by the trap, shocked by the prod, exposed to an airblast from the tube, or to a flash of the bulb, buried the respective source of aversive stimulation with the bedding material, even when a comparable control object was present during conditioning and testing. Thus, the phenomenon of defensive burying is not restricted to situations in which neutral objects serve as the source of painful electric shock. Rats seem to enter the experimental environment with an already established tendency to bury some objects (unconditioned defensive burying) but not others, and they readily learn to selectively bury an object that has been the source of any one of a variety of aversive stimuli (conditioned defensive burying).