Researchers have discovered gamers' brain activity is different when they thought they were playing a human opponent or not, and that this difference is more pronounced in males:
Those data were obtained fairly simply. A dozen males and an equal number of females were subjected to functional MRI scans, which can identify areas of the brain that are active during a given process. In this study, the process was a game, the generalized form of the Prisoner's Dilemma, in which two players get rewards for cooperation while facing the constant lure of gaining at the expense of your opponent. In every case, the subject was actually pitted against a computer opponent that was programmed to make its choices randomly but, in half the tests, the subjects were told they were playing another human.
This gave the researchers the opportunity to compare the two circumstances. Average the two sets of results, and then subtract the areas activated in the human vs. computer situation from the human vs. (fake) human data—the end result should be an identification of any areas of the brain that are activated when people think they're facing a human opponent. In this case, the areas that this process identified are the anterior cingulate cortex, the temporo-parietal junction, and the medial prefrontal cortex.