The idea that experience alters the adult brain in fundamental ways has finally become accepted, so the battle lines have formed around which aspects of brain function are too basic, too hard wired, for experience to change them. Whenever someone asserts that one or another function is fixed and beyond the reach of experience, I refer them to a study finding that the visual cortex—which you’d think is as hard-wired as hard-wired can be—can adapt to an environment of visual deprivation and segue into processing tactile and auditory sensations, as scientists reported last year.

It shouldn’t surprise anyone, then, that playing action video games can also alter the brain, especially circuits involved in vision, attention and other skills you bring to bear when you play games such as Halo or Call of Duty 2. But in a study being published online this afternoon in the journal Nature Neuroscience, scientists are reporting that playing action video games improves an aspect of vision that was thought to be pretty much fixed—namely, contrast sensitivity.

That’s the ability to detect tiny changes in shades of gray against a uniform background, and is something you need to deploy when driving at night or in poor-visibility conditions. You lose it with age, but amblyopia (“lazy eye”) can also impair contrast sensitivity. The only way to fix, supposedly, is with glasses or surgery.

But maybe not. Expert action-video-game players, Daphne Bavelier of the University of Rochester and colleagues find in the new study, have better contrast sensitivity than people who play non-action video games. To make sure that that correlation did not reflect a tendency for people with sharp contrast sensitivity to gravitate toward action games more than people with poor contrast sensitivity do, the scientists gave the non-players intensive daily practice in playing action games. After 50 hours of play spread over 9 weeks, these players’ contrast sensitivity improved. There was no such improvement after playing non-action video games such as Sims.

In 2003, Bavelier found that playing action video games can improve selective attention, as she and a colleague reported in Nature (gotta keep alert for the incoming missile!). But scientists have long suspected that selective attention is trainable. Contrast sensitivity, however, was thought to be something nature makes you good or bad at, something it took away as you aged, and something beyond the reach of training. Apparently, that’s not so. Even more intriguing, its deterioration may not be due solely to things happening in the eye. Improvements can come about by tapping the brain’s power of neuroplasticity, strongly suggesting that deterioration reflects events in the brain and not (just?) the eye.

If you want to immerse yourself in the power of video games to change the brain, Bavelier and two colleagues have written an excellent book chapter summarizing their and others’ findings, including how action video games improve players’ ability to read small print and—ironically, given the terrible reputation video games have among many educators—engage selective attention.