Date of Award


Degree Type


Degree Name

Doctor of Philosophy


The purpose of the present research is to investigate the overjustification phenomenon whereby a person who performs an intrinsically interesting activity for an expected, external reward sometimes decreases his or her subsequent interest and engagement in that activity. The determinants of this effect have important implications for the type of contingency payment and reward systems used in organizational psychology and education where sustaining intrinsic motivation is a central concern.;Currently two main explanations of the overjustification process have been given: the self-perception overjustification hypothesis, and cognitive evaluation theory. Research that has been done to assess the validity of these explanations is reviewed and it is concluded that they are inadequate. Consistent with recent research in affect, a novel approach to the overjustification paradigm is taken in the present research. Specifically it was proposed that negative affect has a critical detrimental influence on intrinsic motivation, either as a reaction derived from self-perception and evaluation processes or as a factor that acts independently of these cognitive activities.;Two studies, using the typical overjustification paradigm, were undertaken to test these hypotheses. In study 1, the overjustification effect was successfully replicated for both behavioral and self-report measures of intrinsic motivation. Importantly, negative affect, measured by the Multiple Affect Adjective Checklist, paralleled these results, and was greatest in those conditions in which intrinsic motivation was predicted and found to be low (i.e., expected reward). In study 2, affect was directly manipulated, independently of the cognitive manipulations, using Velton's mood induction technique. The results showed that the induced positive affect erased the decrease in intrinsic motivation seen in study 1.;The findings are interpreted as support for an affective interpretation of the overjustification phenomenon. More generally, it is suggested that what determines the maintenance of intrinsic interest in any activity is the amount of negative affect that becomes associated with the activity from whatever source. Possible explanations as to how this affective process may influence future behavior are discussed, as are the implications for future research in intrinsic motivation, cognitive behavior theories and organizational psychology.



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