Forbidden Toys

Effect of the severity of threat on the devaluation of forbidden behavior

Aronson & Carlsmith  (1963)

Abstract:

If a person is induced to cease performing a desired action through the threat of punishment, he will experience dissonance. His cognition that he is not performing the action is dissonant with his cognition that the action is desirable. An effective way of reducing dissonance is by derogating the action. The greater the threat of punishment the less the dissonance—since a severe threat is consonant with ceasing to perform the action. Thus, the milder the threat, the greater will be a person’s tendency to derogate the action. In a laboratory experiment 22 preschool children stopped playing with a desired toy in the face of either a mild or severe threat of punishment. The mild threat led to more derogation of the toy than the severe threat.

http://en.wikipedia.org/wiki/Cognitive_dissonance#Forbidden_toy_experiment

Also see Mistakes were made (but not by me)