Effects of age on novelty reactions and exploration in rats

Female rats of three ages (approximately 39, 160 and 316 days) were individually observed in an exploration box which consisted of a novel and a familiar half. By means of a behaviour-sampling technique it was recorded which half of the box the rat was in and what sort of activity it was engaged in at the end of each of 90 10-sec. periods. The number of 8 × 8 in. units entered was also recorded. All rats were seen in the novel half more often than in the familiar half and this novelty preference was greatest for the youngest rats. However, exploration and inter-unit locomotion scores tended to be lower with the younger animals. For all three groups these two scores showed a significant decrement during an observation period.