can cause a greater impact than you might speculate. Researchers placed several subjects in special motion-capture suits, then presented the subjects with a body that had adult proportions or childish proportions, even though both bodies were the same size.
The result was that participants in the childlike bodies were more likely to identify as children rather than as adults, exploring more child-like environments and behaving less like adults. It's worth keeping in mind that these behaviors happened within motion-capture suits designed to simulate actual movement in virtual bodies, so how much of this would transfer to MMOs is questionable. But it's an interesting set of variables to consider, especially in terms of how much we identify with our avatars in the game.
[Thanks to David for the tip!]