EXPERIMENTS ON ‘NEOPHOBIA’ IN WILD AND LABORATORY RATS

Abstract

All rata ( Rattus norvegicus ), wild or tame, have a well‐marked tendency to explore their surroundings. Wild rats, but not tame ones, also tend to avoid unfamiliar objects in a previously explored, and therefore familiar, area. The effect of environmental change on feeding was studied in three groups of wild rats. Bats of Group 1 were accustomed to feeding from a wire basket at the back of the cage; for them the change consisted of transfer of the food to an unfamiliar tin at the front of the cage. Group 2 had food in the basket throughout, and the change consisted only in an empty, unfamiliar tin being put in the front of the cage. The rats of Group 3 fed from a basket in the front of the cage; the change for them was the placing of an unfamiliar empty tin between the back of the cage, where they slept, and the food. In all three groups feeding was interrupted by the change. In the first group, three of the five rats stopped eating completely for one or more days; in the other two groups, food consumption was merely reduced on the first day after the change. The check in eating was not due to exploration: the new object was at first completely avoided by all the rats. Tame albino and hooded rats, subjected to the same procedure as the wild rats of Group 1, investigated the tin and the food in it at once; their food intake during the day after the change was unaffected. The first approach of the hooded rats to the new object was, however, more hesitant than that of the albinos. Investigation of a new object, or new conditions, can sometimes lead to an interruption of feeding in tame rats, but this has nothing in common with avoidance behaviour in wild rats.