AGE, INCENTIVES, AND MAZE-LEARNING BY HYBRID MICE

C47BL/6J, DBA/2J, B6D2F1, and B2B6F1 mice (N = 20 per group) were trained on the Lashley III maze at 60 days of age with water, oatmeal, mash, or cheese as the incentive. There was a strong dominance effect on three tests, but not on that with cheese, indicating that dominance and heterosis effects are influenced by environmental factors. Two groups were tested at 120 days with water and oatmeal. The hybrids did not manifest heterosis, and additivity supplanted dominance as the major effect at 120 days. The findings suggest a change in the set of genes controlling maze learning between 60 and 120 days.