Surely, giving out incentives must be one of the most traditional and frequently used ways for motivating others. So why did this happen?
The reason for this may be because of effort justification and overjustification.
Effort justification is a way to reduce cognitive dissonance and is when people are more likely to like what they are doing if they have worked hard for it. While overjustification is when intrinsic motivation within a person is undermined in situations when people are told that they are doing it for an extrinsic reward.
In 1975, Lepper & Greene asked 80 pre-school students to participate in their study on investigating the effects of extrinsic rewards on intrinsic motivation. In the study, the students were asked to play with a set of puzzle. They were then divided into two groups. The students in the expected reward condition were told that if they were able to complete the puzzle, they will be able to play with other toys; while the students in the unexpected reward group were not told about the toys. They have found that even though the expected reward group have completed their puzzle in a shorter period of time, they are also significantly less likely to continue to play with the puzzle later on (refer to Figure 1).
The results from this study also coincide with their previous study which was done in 1974, when they asked children to draw pictures. They have found that the expected award group drew more pictures than the no award group, but the pictures drew by the expected award group were also of lower quality (refer to Table 2).
Not only do the results from the two studies imply that the effect of extrinsic rewards is short lived, it also provide evidences for effort justification and overjustification. These two ideas suggest that when we work hard, we tend to internally justify our hard work as intrinsic motivation, that we are doing it because we like it and we hold great interest in it. However, if we know beforehand that we are going to be rewarded, especially when the extrinsic reward is unrelated to the action, our hard work will be externally justified, that we are doing it just for the reward, not because we like it. In this case, this is shown by the lack of students continuing with the puzzle and the quality of drawing in the expected award group.
Hence, if you want to your child to succeed in their studies in the future, it is more important to motivate them to develop their interests rather than using rewards to improve their actual performance. The effect of incentives are short-lasting, they will only work if they are really what the child wants, and if they increase each time you reward them. However, if you develop their interests, they will naturally work hard and success will also follow.
Greene, D. & Lepper, M. R. (1974). Effects of extrinsic rewards on children's subsequent intrinsic interest. Child Development, 45, 1141-1145
Lepper, M. R. & Greene, D. (1975). Turning play into work: effects of adult surveillance and extrinsic rewards on children's intrinsic motivation. Journal of Personality and Social Psychology, 31, 479-486