>
> In fact, I hear studies have shown that such rewards often result in
> the opposite of the intended effect. But I know little about these
> studies.
Yes, it's well documented that ample praise and attention undermines children's intrinsic interest in activities. This may seem counterintuitive, but it's based on our need for self-justification: if I do X and I receive ample praise and reward, I will tend to explain to myself by saying--"I do it for the external rewards". If I do X and I receive less praise and rewards, but I continue doing it, then--"I do it because it's interesting/important to me".
In sum: the best way to kill anyone's genuine love for something is to--give them huge amounts of external rewards/praise when they do it.
(This area of research in social psychology is another reason why I have little patience with the "utility maximizing agent" fairy tale so common among economists.)
Miles