When some task is presented as prerequisite for something else- that is, a means towards some other end- the task comes to be seen as less desirable. It also conveys the message to the kid, that if teachers have to bribe him to do this, it must be something that he wouldn't want to do, and/ or the activity itself is not worth doing for its own sake. The only reason he is doing it is for the reward.
Kids who were invited to play with another child so that they could get access to his toys or were offered cookies for playing with the child, were less interested in playing with the other child on future occasions.
In one representative study, young children were introduced to an unfamiliar beverage called kefir. Some were just asked to drink it; others were praised Those children who received either verbal or tangible rewards consumed more of the beverage than other children, as one might predict. But a week later these children found it significantly less appealing than they did before, whereas children who were offered no rewards liked it just as much as, if not more than, they had earlier.
There is a story of an elderly man who was harassed and insulted by a crowd of 10 year olds as they passed his house on their way home from school. One afternoon after listening to their insults – how stupid, bald and ugly he was , he came up with a plan. He announced to the kids that if they came back tomorrow he would pay them a dollar each for their efforts. Amazed and excited they arrived even earlier and began throwing insults with much fervor. The old man , true to his word paid everyone his dollar. He then announced – do the same tomorrow and you will get 25 cents for your trouble. The kids thought that it was still worth their while and came back the following day to taunt him .At the first catcall, he walked over with his quarters paid off his hecklers. From now on, he announced I can only give you a penny for doing this. The kids looked at each other in disbelief. ' A penny – forget it ' and they never came back.
Two groups of kids were asked to evaluate and give their opinions about a collection of puzzles after playing with them for half an hour. One group was paid by the company for their time. When the half an hour was up , all but one of the kids from the reward group stopped playing with the puzzles . Kids from the non-reward group had to be pulled away from the puzzles. Rewards got in the way of the kids developing any interest and intrinsic reward in doing the puzzles.