The effect of age, sex, and a prematurely induced puberty on the solving of Maier's three-table test by rats has been investigated.

It is found that rats 70-90 days of age are able to solve the problem more successfully than rats 30-70 days of age, unless the animals are fully adjusted to the experimental procedure. When fully adjusted, rats 30-50 days of age can solve the problem more successfully than animals 50-90 days of age, and just as successfully as the adults previously investigated by Maier.

Post-pubertal females have been found to be less successful in problem solving than post-pubertal males. The cause of this difference appears to lie in difference in the adjustment of animals to experimental procedure, and not primarily to differences in ‘reasoning’ ability.

Dr. Hanson did not receive the final proofs of this paper; he had previously expressed his indebtedness to Prof. S. Zuckerman for his advice and encouragement throughout this study.