Jodi L. Whitaker and Brad J. Bushman, in their new original reserach article "Boom, Headshot!": Effect of Video Game Play and Controller Type on Firing Aim and Accuracy, have drawn the following conclusion:
Video games are excellent training tools. Some writers have called violent video games "murder simulators." Can violent games "train" a person to shoot a gun?
…Participants who played a violent shooting game using a pistol-shaped controller had 99% more headshots and 33% more other shots than did other participants… Habitual exposure to violent shooting games also predicted shooting accuracy. Thus, playing violent shooting vidoe games can improve firing accuracy and can influence players to aim for the head.
Those who played the shooter that rewards headshots passively learned to aim at the head areas on targets in real life, though it's actually better to aim for the upper chest area.
The trouble with the study, however, is the choice of Resident Evil 4 as that video game. Even if players use a realistic-looking controller, Resident Evil 4 is far from being a realistic shooter with a laser-sighted gun while shooting sluggish humanoid zombies. Another shooter like Operation Flashpoint or even Rainbow Six would have been better choice. Also, participants only played Resident Evil 4 (as well as Wii Play and Super Mario Galaxy) for 20 minutes before heading off to the real firing range.
However, the research does show that playing a violent first-person video game increases accuracy and "especially at the head". Of course, it's important to note that their results "do not indicate that a person who plays violent shooting games is more likely to fire a real gun at a person". All we can say is, if that person tried… less ammo would be wasted.