Economists believed that if people are paid for carrying out tasks that they like to do, their rewards will increase. Psychologists believe that the payment will crowd out (reduce) the intrinsic reward, and people may not take up the task if the payment is stopped.
Research experiments conducted previously (calculating time taken, output and productivity) seemed to prove that psychologists’ theory is correct, but new research showed that there were flaws in the earlier research (all 3 variables were not considered, the variables themselves are conflicting, the studies were small). New research also showed that intrinsic enjoyment is not crowded out by payment, but it may reduce the quality of the evaluation.