The subjects, 4-, 6-, 8-, and 10-year-olds, were tested with 144 two-trial object-discrimination problems in a six-session learning-set procedure. Each child was tested with two types of problems. A single stimulus was presented on Trial 1, rewarded on half of the problems and not rewarded on the remaining problems. On Trial 2 the stimulus was again presented, paired with a new stimulus. Children were required to respond according to a winstay, lose-shift principle. The 10-year-olds met criterion for both types of problems rapidly in contrast to the younger children, who showed very gradual improvement. The win-stay problem was significantly more difficult than the lose-shift problem and age did not significantly interact with type of problem presented. However, during the six sessions 6-and 8-year-olds showed more improvement than 4-year-olds, particularly on the more difficult win-stay problem.