Acquisition of a matching-to-sample task in young and middle-aged male and female rats.

Male and female rats were trained in a water-reinforced matching-to-sample task. The rule was acquired more rapidly by the females. After initial training, the retention of the rule was measured when the rats were twelve and 14 months old. The performance of neither group was modified at twelve months, but at 14 months, while no change appeared in the performance of males, females showed a drop in correct responses. Training in a modified device which made the task more difficult induced no changes in performance. Final training (at 18 months) showed the drop in performance in females had persisted. The decline of performance in middle-aged females might be related to the ageing female reproductive system.