QUARTERLY JOURNAL OF ECONOMICS ents yield ambiguous results. It has been (Walster, Walster, and Berscheid, 1977, p 124] that this ambiguity occurs because it is less costly for overpaid agents to increase the psychological evaluation of their labor inputs than to increase actual input. These experimental results are consistent with the hypothesis that overpayment does not increase input, and thus that While much less work has been done on underpaid subjects, several studies have obtained supportive results. In one revealing study Lawler and O' Gara [1967] compared the performance of workers who were paid the"going " rate of 25 cents per interview with the performance of interviewers who were seriously underpan at the rate of 10 cents per interview. The underpaid interviewers conducted far more interviews that were on average of significantly lower quality. Psychologically the lower paid interviewers also had reduced self-esteem--suggesting that workers adjust not only the amount of effort but also their perception of the quality of the labor input when equity is not realized. In a clever experiment Pritchard, Dunnette, and Jorgenson [1972] hired men to work for a fictitious Manpower firm they ealistically set up for their experiment. After the workers had been at work for three days, the firm announced a change in their method of pay. Subjects'earnings were variously adjusted upward or downward. Those subjects with downward adjustments expresse considerable job dissatisfaction on a questionnaire and also per formed less well in their work after the change In a similar experiment Valenzi and Andrews [1971] hired workers at $1.40 per hour, but then announced that, due to the budgetary process involving their grant from the National Institute of Mental Health orkers would receive more than the stipulated $1.40, and some would receive less. Twenty-seven percent of those who were given the lower wage of $1.20 quit immediately-a result consistent with an upward sloping labor supply curve but also explained by the workers anger at their unfair treatment In what is probably the most revealing experiment, Schmitt and Marwell [1972] gave workers a choice: whether to work coopera tively in pairs or to work alone. When pay was equal, workers chose to work in pairs. However, workers were willing to sacrifice signif cant earnings to work alone when the pay in pairs was unequa consider this implication of equity theory obvious; some expe alerta tive e planations tradodtmoans and friede ry, but in all cases there are easy man,1971]