The role of self- and other-animal-produced odors in rats’ preferences for novelty in an exploration box

Abstract

Following confinement to one half of an exploration box, rats were faced with both halves (novel and familiar) after each half had been washed or not. When both halves had been washed, thereby decreasing the likely influence of odors arising from the earlier presence of the subject or previous occupants, neither was preferred. When only the novel half had been washed, thereby ensuring that odors were available in the familiar half alone, familiarity was preferred. However, the novel half was preferred when it contained odor cues originating from earlier occupants, and the familiar half contained no cues or cues from occupancy by the subject either alone or in combination with those from previously tested animals. The greatest preference for novelty occurred when the familiar half contained self-produced and the novel half contained other-animal-produced odors. Apparent effects of the washing procedures on rearing and locomotion were accounted for by behavioral changes that enabled the chosen half to be occupied. Since in a second experiment differences in brightness discriminability of the two halves of the apparatus did not affect novelty preferences, it was concluded that choices were made primarily on the basis of rat-produced ol-factory information. When the exploration box technique described here is applied, this conclusion should be taken into consideration as one attempts to interpret the effects on novelty choices of pharmacological and surgical procedures likely to interfere with central olfactory mechanisms.