nd now, the news that every parent dreads. Researchers are reporting today that first-person-shooter video games — the kind that require players to kill or maim enemies or monsters that pop out of nowhere — sharply improve visual attention skills.

Experienced players of these games are 30 percent to 50 percent better than nonplayers at taking in everything that happens around them, according to the research, which appears today in the journal Nature. They identify objects in their peripheral vision, perceiving numerous objects without having to count them, switch attention rapidly and track many items at once.

Nor are players simply faster at these tasks, said Dr. Daphne Bavelier, an associate professor of cognitive neuroscience at the University of Rochester, who led the study. First-person action games increase the brain's capacity to spread attention over a wide range of events. Other types of action games, including those that focus on strategy or role playing, do not produce the same effect.

While some researchers have suggested possible links between video games and other abilities, this study is thought to be the first to explore their effects on visual skills. Though the number of subjects was small, Dr. Bavelier said, the effects were too large to be a result of chance.

"We were really surprised," Dr. Bavelier said, adding that as little as 10 hours of play substantially increased visual skills among novice players. "You get better at a lot of things, not just the game," she said.

But Dr. Bavelier emphasized that the improved visual attention skills did not translate to reading, writing and mathematics. Nor is it clear that they lead to higher I.Q. scores, although visual attention and reaction time are important components of many standardized tests.

"Please, keep doing your homework," said Dr. Bavelier, the mother of 6-year-old twins and a 2-year-old.

Dr. Jeremy Wolfe, the director of the Visual Attention Laboratory at Harvard Medical School, who was not involved in the study, said he was intrigued at the idea that "socially dubious games might improve something like general intelligence."

"It might give every 14-year-old something to tell his parents," Dr. Wolfe said. " `Hey, don't make me study. Give me another grenade.' "

Still, he noted that an increased capacity for visual attention was helpful in tasks as diverse as flying, driving, radiology and airport screening.

Dr. Bavelier is an expert on how experience changes the brain, particularly the effects of congenital deafness on visual skills and attention. A few years ago, a Rochester student, Shawn Green, asked to work on a senior project in her laboratory. They agreed that he would help design visual attention tasks for the deaf.

But when Mr. Green tried out the tests, he found they were ridiculously easy, Dr. Bavelier said. So did his friends, who were all devoted to video games.

The professor and her student decided to study the connection between video game playing and visual attention. They carried out four experiments on undergraduates, all of them male because no female shooter game fans could be found on campus.

The first tested the ability to localize targets in a cluttered environment and spread visual attention over a wide area — a skill that many elderly drivers lose. Gamers performed at least 50 percent better than nongamers, Dr. Bavelier said.

The second involved the ability to say, instantly, how many objects were flashed on a screen. Most people can do this with up to four objects, Dr. Bavelier said. Above that, they start counting. Gamers could identify up to 10 items on a screen without counting.

The other two experiments tested the players' ability to process fast-occurring visual information and to switch attention. Again, players were far superior to nonplayers.

A fifth experiment trained nonplayers, including some women, for 10 consecutive days on one of two video games — either Medal of Honor: Allied Assault, a first-person-shooter game that simulates World War II combat situations, or the slower-moving puzzle game Tetris. Only the shooter game improved visual attention, Dr. Bavelier said, and it did so in both sexes. Among novices, the effects waned within a couple of months, but superior visual attention skills seemed firmly rooted in game addicts.

Dr. Bavelier said the next step would be to tease the games apart to find out what aspects promoted brain changes. Are violence and danger necessary? Does this sort of brain plasticity change with age? Will it affect certain measures of intelligence?

Meanwhile, she said, the military is already exploiting action games to train special forces.

"To enter territory you've never seen and detect where your enemies are," she went on, "you need an accurate understanding of the visual scene."