In an experiment, children who were given praise and certificates for drawing spent more time drawing than children who were not rewarded. Later, when no external rewards were available, these same children spent less time drawing than did the unrewarded children. This effect is called effect.

the overjustification.                                                                                            

Explanation:

Overjustification effect: In psychology, the term "overjustification effect" is described as one of the phenomena in which an individual is being rewarded for performing or doing something tends to diminish "intrinsic motivation" of doing or performing that action or behavior. However, it can often lead to putting a serious impact on an individual's behavior and motivation.

In the question above, the given statement represents the overjustification effect.

speed

explanation:

b. the american revolution