This study was designed to test two major hypotheses: (1) Validity of expectation is an increasing monotonic function of development. (2) Invalidity of expectation is more a function of overestimation of hedonistic tendencies than a function of underestimation. A total of 277 middle class children in the first, fourth, and fifth grades were given two trials on a task to which high feedback was attached and two trials on a different task with which low feedback was associated. They were then presented with a final task, resembling either the high or low feedback tasks just completed. Subjects were asked to indicate the score they expected to attain. Study results supported both major hypotheses and emphasized that overestimation or hedonistic expectations are a decreasing monotonic function of grade in school, and sex differences were virtually nonexistent for subjects in this sample. The developmental function demonstrated in this experiment suggests that if valid expectations are a major component of human motivation, the manipulation of validity of expectation in children warrants attention. (ED)