The spreadsheet was seven feet long. Printed in nine-point font were the names of the perpetrators of mass killings, the models of weapons each had used, and the number of victims. The gruesome document was discovered at the home of Adam Lanza, who on 14 December 2012 fatally shot his mother, before killing 20 children and six teachers at the Sandy Hook Elementary School in Connecticut, and turning his assault rifle on himself.

It took only a few hours for the authorities to link the massacre to Lanza’s playing of violent video games. "[People heading the investigation] don't believe this was just a spreadsheet," a police officer later told the New York Daily News. "They believe it was a score sheet. This was the work of a video gamer, and it was his intent to put his own name at the very top of that list."

Lanza's shooting spree was just the latest of a long list of violent crimes that have blamed on video games. Scientists have evidence that virtual violence can trigger aggressive thoughts and anti-social behaviour, but most reject the idea that gaming can turn otherwise balanced individuals into killers.

A growing body of research is showing the flip side, though – video games can help people see better, learn more quickly, develop greater mental focus, become more spatially aware, estimate more accurately, and multitask more effectively. Some video games can even make young people more empathetic, helpful and sharing. As public debate on the subject is often highly emotive and polarised, and as more and more of us are becoming gamers, researchers say it is important to move beyond the generalisations that characterise much of the discussion.

"We know there are good sugars and bad sugars, and we don't discuss whether food in general is good or bad for us," says Daphne Bavelier, a neuroscientist at the University of Rochester, New York. "We need to be far more nuanced when we talk about the effects of video games."

Douglas Gentile at Iowa State University, US, agrees. "Game research has tended to get sucked down into a black hole of people yelling at each other, saying either games are good or games are bad," says Gentile, who studies the effects of video games on physiology and behaviour. "I think we are starting to move beyond this inappropriately simplistic idea to see games can be powerful teachers that we can harness."

Multi-level field

Part of this has stemmed from the fact that 20th-Century video gaming research often failed to distinguish between game genres. Studies lumped together the different brain processes involved when racing cars, shooting baddies, street fighting, and completing puzzles. But with the benefit of hindsight, researchers now recognise they hold only limited insights into the impacts of video games.

Bavelier stumbled upon the particular effects action games may have on the brain by accident. She was designing a test to probe the effects of congenital deafness on visual attention, and while trialling it a young researcher in her department, Shawn Green, and his friends repeatedly scored far higher than expected. Eventually they realised their exceptional performance could be traced to their fondness for the action games Counter-Strike and Team Fortress Classic.

Bavelier and Green hypothesised that this type of game had distinct effects on the brain because achieving a high score requires players to react quickly, while processing information in their peripheral vision, multi-tasking, making predictions and processing the constant player feedback. In research published in 2003, they used a series of visual puzzles to demonstrate that individuals who played action games at least four days per week for a minimum of one hour per day were better than non-gamers at rapidly processing complex information, estimating numbers of objects, controlling where their attention was focused spatially, and switching rapidly between tasks.

Was this cause or effect, though? Were the games improving people’s focus or were people with good attentional focus simply more likely to play action video games?, Bavelier and Green asked non-gamers to play the first-person shooter game Medal of Honor for one hour a day for 10 days, and found their ability to focus on environmental cues improved much more than those in a control group who played the classic puzzle game Tetris. Additional tests from other researchers came to similar conclusions. For instance, Joseph Chisholm, a psychologist at the University of British Columbia, Canada, found action video game players were better able to identify distraction and quicker to return their focus to the main task.

Bavelier wanted to pin down more precisely why action gamers appear to have better focus. She placed electroencephalography (EEG) headsets on gamers and non-gamers, and asked them to watch a screen on which three rapid sequences of letters appeared simultaneously. They were told to focus on one of the three and press a button when numbers appeared, while ignoring distractions. The EEG headsets tracked electrical signals in the brain, allowing Bevelier to measure how much attention the volunteer was allocating to the task and to the distraction. Gamers and non-gamers were equally able to focus their attention on the target sequences, but the gamers performed better and had quicker reaction times. "The big difference was action video gamers are better at ignoring irrelevant, distracting visual information, and so made better decisions," she says.

Her team has also shown that action gamers may have stronger vision. They can better distinguish between different shades of grey, called contrast sensitivity, which is important when driving at night and in other poor visibility situations, and is affected by ageing and undermined in those with amblyopia, or "lazy eye". They also have better visual acuity, which is what opticians measure when they ask you to read lines of ever smaller letters from a chart at distance.

Bavelier found action video games could also improve the vision of non-gamers. She asked groups of non-gamers to play 50 hours of Unreal Tournament 2004 or Call of Duty 2, or to play the slower, non-action game, The Sims 2, over nine weeks. By the end of the study, the contrast sensitivity of those who trained on action games had improved more than those who played The Sims 2, and the benefits lasted for at least five months. Other researchers at the University of California, Berkeley, showed that adults with lazy eyes who spent 40 hours playing video games with their good eyes patched could improve their ability to distinguish smaller letters on such charts. The higher scores were not seen in those asked to do other visually demanding tasks such as reading and knitting with their good eyes patched.

Power of empathy

Researchers know from years of studies that when men and women are given the task of rotating two-dimensional and three-dimensional objects in their heads, men tend to perform better than women. When Jing Feng, a psychologist at the University of Toronto, in Canada, and colleagues asked a small group of non-gamers to play either Medal of Honor or the 3D puzzle game Ballance for 10 hours over several sessions, they were surprised by the results. They found the action game training boosted the scores of the female participants more than it did the males, and the effect of the training was still apparent five months later.

"We already knew that there are gender differences in mental rotation but it was interesting to see they exist in our ability to effectively distribute attention in space, and more importantly that this is something that can be diminished through playing action video games," says Feng. "If we could extract the critical training components from first-person shooter games, I could see ways to develop spatial-skills training tools to address gender differences in fields like engineering and information technology."

So if playing video games can lead to beneficial brain changes, does this positively affect behaviour? Gentile set out to find out by testing the effects of playing "pro-social" games on young people in the US, Singapore and Japan. The children and teenagers in each study were more likely to help others in real life or in simulated tasks if they played the games where the characters co-operated, helped one another, or pitched in to clean a virtual neighbourhood. When American students were asked to select 11 puzzles for a partner to complete and were told their partners would get $10 gift vouchers if they completed 10 of them, the pro-social game players were much more likely to choose easier puzzles than those who played violent games.

"Video games are neither inherently good nor bad," says Gentile. "When we play games we want to be affected in some way, otherwise it would be boring. What we now know is that across cultures and age groups computer games can either cause problems or be beneficial, depending on its content."

Gentile’s findings are supported by a study conducted by Tobias Greitemeyer, now at the University of Innsbruck, Austria. He asked 46 German students to play Lemmings, in which players must protect groups of rodents from dangers, or Tetris. They were then asked to complete three unfinished stories that included one about a driver and a cyclist who narrowly avoid a collision; another about two friends, one of whom is unapologetic despite being always late; and a third one about a customer speaking to a restaurant manager after waiting an hour to be served and having food spilt on him. People who played Lemmings suggested less aggressive endings.

Questions still remain about how long any effects could last. Gentile recently completed a study involving 3,000 schoolchildren, studied over three years. He expects to publish the results later this year. "What we are finding is that pro-social games affect children's sense of empathy," he says. "As they become better at noticing the feelings and reactions of others, and act in more helpful and caring ways within games, this seems to affect how in tune they are with others, and how they behave in real-life. With violent games we see the exact opposite."

Gaming systems

Taken as a whole, the research poses a problem for those hoping that video games can provide a path to smarter, kinder young people. Action games are high among the best-sellers, but they involve a lot more fighting and killing than caring and sharing.

This does not put those in the field off. Bavelier, for example, recently received a US National Science Foundation grant to create, in collaboration with educational games company E-line Media, an action game for 8-to-12 year olds that improves their ability to rapidly estimate numbers – a skill that correlates with improved mathematics performance.

Meanwhile Richard Davidson, a neuroscientist at the University of Wisconsin-Madison, is leading a project to develop two games to help 11-to-14 year olds develop greater empathy, co-operation, mental focus, and self control. In Tenacity players progress through the game by keeping track of their own breathing, which helps children develop mindfulness. In Crystals of Kaydor, players must understand the emotions of aliens and respond helpfully to win. The games are being tested in randomised trials that began in May.

Davidson is well aware that many previous efforts to develop games that are good for us have resulted in titles that players don't want to play. But he knocks those failures up to academics who don't have the required skills or resources to develop an irresistible game.

“We have had a team of 12, including some of the best game designers in the country, working on these games for a year,” he says. “I believe you can have fun and have beneficial effects at the same time." Media entertainment businesses have also decided the industry would benefit from greater links with neuroscientists and psychologists, and that by collaborating with academics they could to bring beneficial and therapeutic games to market.

Ultimately, however, it will be down to consumers, or their parents, to decide whether they play the games scientists say are good for them. "Our brains are constantly being shaped by the actions we engage in and our environment, and most of that influence is unwitting," says Davidson. "Playing games today is like being in a rudderless boat. Gaming presents us with an opportunity to take greater control over the shaping of our own minds and brains. I think going forward most parents will want their children in boats with rudders."

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