In a 1964 investigation of the effects of age and memory on problem solving, using subjects from age three to age nineteen, it was found that the youngest and oldest subjects performed a three-choice probabilistic task significantly different from the "middle-age" children (7 to 9 years old). The three-choice task was an apparatus with a signal light, three buttons, and a container into which marbles were dispensed for "correct" responses. Only one button was set up to release a marble, and even it was on a partial reinforcement schedule. The younger and older subjects tended to maximize their choice of the "pay-off" button. The middle-age children tended to respond in simple patterns regardless of the fact that such patterns did not increase the pay-off. It was thought that this result interfered with their memory in regard to which button was paying off. A later study, in which a memory aid was used for half of the subjects, was conducted. It was found that the younger and older subjects performed about the same as before, regardless of the existence of the memory aid. The 7- and 9-year-olds who used the aid performed significantly better than those who did not. A third study, similar to the previous studies except that four different reinforcement schedules were used, indicated that responses become more complex with age. (WD)