Goal theory postulates that harder goals lead to higher performance than do easier goals. The present study tested the prediction, based on expectancy valence theory, that this would be true only if the payoff for succeeding at the harder goal is sufficiently greater than the alternatives to compensate for its greater difficulty. Sixty-three undergraduates were each given an easy and a hard task/goal, requiring the comparison of paired sets of three-digit numbers. Expectancy theory measures for the two goals were obtained from the subjects. Performance was higher for the hard goal than for the easy goal, supporting the goal theory postulate. Force was also higher for the hard goal than for the easy goal. In addition, force change across the two goals was associated with performance change, supporting the conclusion that expectancy valence theory can predict the goal theory postulate. The valence of goal attainment was higher for the hard goal than for the easy goal. Valence change across the two goals was associated with performance change to a greater degree than was expectancy change, suggesting that the attained performance difference can be attributed to the valence difference. [ABSTRACT FROM AUTHOR]