The function of the brain in olfaction I. Olfactory discrimination and an apparatus for its test

Rats average 83 trials to learn a simple olfactory discrimination. The apparatus employed depends upon two interchangeable entrance boxes to a food compartment, each box being filled with scented wood shavings through which the animal has to dig in order to enter. One of the boxes is blocked; the animal learns to choose the open box on the basis of its odor. Performance of the discrimination, when learned, is clear; also, it is stable from the point of view of both retention and overtraining. Several odors were successfully tested. Excision of the olfactory bulbs, histologically verified, and other controls, indicate that the rats use olfaction exclusively as the cue for the discrimination.