Video games are the biggest form of entertainment in the world, but sometimes they bleed into people's lives offline in surprising and disturbing ways.

Christian Dines' hands were twitching. As though he were still gripping his video game controller, about to make a killer move. But the game was switched off and his hands were free. The US-based sustainability advisor had also noticed how, when he glanced at objects in his room, he felt an urge to absorb or "collect" them, like weapons or power-ups in his game.

He swallowed hard. "I thought, 'what the hell is this?' It was something I'd never experienced before as a gamer," he says. After a week of playing the same game maybe two or three hours a day, Dines' virtual experience was spilling over, disturbingly, into reality. 

"It all only lasted a couple of days, but the effect was disorientating," he recalls. "It's unnerving to be distracted in some way by a screen when you're no longer in front of it."

Dines had, it seems, experienced something called Game Transfer Phenomenon, a condition in which the physical world and video games bleed together. While this might not be very common, for gamers who experience it, the condition can be extremely unsettling. And potentially even dangerous.

The term Game Transfer Phenomenon, or GTP, was first coined by Angelica Ortiz de Gortari, a psychologist at the University of Bergen in Norway. She first proposed the concept a decade ago while working on her doctoral thesis under the supervision of Mark Griffiths, head of Nottingham Trent University's International Gaming Research Unit. Ortiz de Gortari was motivated by her own experience of GTP. One day, she was walking around her local supermarket and realised that she was imagining peering at products on the shelves through a rifle scope.

"I thought, 'Wow! This is interesting'," she recalls. "A phenomenon that changes your perception by encouraging you to see objects through the lens of the game you're playing," she says, adding that her response had felt involuntary, leaving her with serious questions about what it meant.

But what exactly is GTP? Ortiz de Gortari suggests that one could compare it to potentially more common experiences such as ear-worms, in which you spend days trying to get a catchy song out of your head. Or when images from a television show you binge-watched keep popping up in your mind's eye. With GTP, though, the intensity is arguably dialled up, says Ortiz de Gortari. Not least because gaming activates brain areas associated with control inhibition – the ability, or not, to control one's thoughts and behaviour rather than acting on impulse. This can also occur while passively watching television, but to a lesser degree than while gaming.

Ortiz de Gortari's studies suggest that GTP induces distress and dysfunction for around half of those gamers who say they have experienced it, with confusion, hyper-vigilance and irrationality among the symptoms. For others the only notable response may be a feeling of embarrassment that their game-play has spilled over into "real life".

One study participant she interviewed reported seeing health indicator bars like those in the role-playing game World of Warcraft floating above their companions' heads. Another spoke of lapses in concentration after not being able to stop "seeing" images from a game. Others said colours in the real world seemed transformed, and began to mimic the colours of a game world they had recently played in. While such effects are usually transitory, GTP can provoke a startling array of spontaneous or involuntary effects, according to Ortiz de Gortari's research.

While rare, these effects can even take the form of involuntary physical actions and behaviours. A game could end up shaping the way one interacts with real world objects or people. For example, a walk down a supermarket aisle could be experienced through the lens of gameplay, with the player perhaps "shooting" at products or people, possibly with a corresponding involuntary physical action in the hands as though working console controls.

In total, Ortiz de Gortari has recorded GTP experiences among gamers related to more than 400 titles of all kinds. Her largest on the subject to date, published in 2024, involved the participation of 623 Chinese gamers, both male and female. The results suggest that between 82% and 96% of those gamers have experienced some form of GTP.

It's possible that some gamers might have endured episodes of GTP but never admitted this to anyone, for fear of being considered "crazy", says Ortiz de Gortari. It is time we demystified GTP, she argues. "The mission for me is to inform people about the phenomenon, to raise awareness, because the [gamers] I've spoken to about it have been very concerned," she says. "Often, people don't want to talk about the experience of, say, seeing things that aren't there with their open eyes – even if that's what happens – because that's to talk about hallucinations, and they're associated with [potentially taboo, severe] mental illness."

Ortiz de Gortari argues that GTP has become a more common experience as games, especially role-playing, simulation, adventure and first-person shooter games, have become increasingly realistic and immersive. They offer sprawling environments full of detail and interaction. Essentially, gamers end up living virtual lives through such media and can find the gameplay deeply affecting.

"The more realistic the video game world is, the more likely players are to confuse the game world and the real world," says Ortiz de Gortari, who adds that this could mean GTP is becoming more common and impactful. The sophistication of games has undoubtedly increased since the days of Tetris and Super Mario, she points out. "Essentially the sophistication of the game facilitates the experience outside of the game."

Ali Farha, a gaming industry commentator and senior game producer at Stockholm-based Star Stable Entertainment, has experienced GTP himself. He describes his case as "a pretty harmless sense of gameplay repeating offline". He suggests that regular breaks during extended stretches of play and a period of conscious decompression after a long gaming session – reading a book or watching some light TV – could help counteract the likelihood of GTP raising its head.

Playing time – particularly above four hours – does appear to be a key factor in the onset of GTP. That's one reason why Scott Jennings, spokesperson for the US-based Gaming Addicts Anonymous (GAA), whose members invariably are at the high-end of playing hours, says the support group is increasingly mindful of this potential side-effect of gaming. 

Farha also says that few people currently appreciate that, as he believes, the bridge between the real and the virtual is actually a two-way street.

"We overlook that we also take the experiences and expectations of the real world into the game world – and that too can be disorientating," he says. "I think it's quite common to enter a multi-player online game and feel loneliness, for example, even though you know you're at home. The experiences we have online become part of our personality. We build memories inside the virtual space of the games we play too, in the same way we build memories in the real world." In fact, studies suggest that games can be more conducive to memory formation than real life.

"I think for a lot of players the virtual and real worlds are starting to blur," Farha adds.

While no-one has reported physical harm as a consequence of GTP to date – GTP could, in principle, endanger someone. "It's not a good idea for me to be trying to kill demons while I'm driving," as Dines puts it.

Exactly why the virtual world can blur with the real world in this way, however, is still not clear. Some studies suggest different brain networks are activated when observing something in a virtual environment, compared to a real one. The same has been found with objects in augmented reality, where virtual elements are superimposed onto the real world. But some studies have shown that human memory can sometimes struggle to recall whether something occurred in a virtual environment or in real life – with the effects being more pronounced when using virtual reality systems.

Ortiz de Gortari has indicated that GTP might be more common among gamers who have a tendency for mind-wandering and have a low working memory capacity. She also believes it could be the result of the game priming the brain or some sort of associated learning effect that when gamers encounter something similar to an environment or scene they came across in a game, it can trigger an involuntary response.

But these are all theories for now.

"The human brain isn't built to differentiate between reality and today's virtual worlds," says a spokesperson for Game Addicts Anonymous. "That's one reason why games are so captivating and why it's no surprise the two experiences overlap."

Jennings also recounts a GTP-like experience. After playing an aggressive racing game he later felt "a disconcerting urge" when out driving, to smash into a vehicle that pulled up alongside him. He argues that GTP could be compared to alcoholism. It's not necessarily about how many drinks you've had but rather it's about your personal relationship to alcohol. Similarly, he says, while most people may have a functional relationship to gaming, some players are less able to contain its effect to playing time.

Recent research by Ortiz de Gortari would appear to back this up. Her findings suggests that certain personality traits are likely a factor in one's propensity towards GTP. Other influences she cites include suffering from sleep deprivation, stress, depression or anxiety.

Max Dzmitryiev, a US-based counsellor and gamer, says he grew up experiencing symptoms of anxiety. Video games, he says, offered an escape from reality. 

"But I'd easily get immersed in them," he recalls. "And as the level of immersion grew, so the stimulation was higher and so I had more GTP experiences," he says. To him, GTP is "freaky and unpleasant" and something that can overwhelm his thoughts and decisions for as long as 20 minutes. After such a bout, GTP can keep popping up for days, intermittently, he explains.

Dzmitryiev has even noticed that watching someone else play a game can induce GTP-style effects. He gives the example of observing someone having fun in Minecraft, a colourful exploration and world-building game. Watching the other person's progress intently can lead to Dzmitryiev to, he says, literally perceiving his own surroundings as though they were built from the cube-like blocks used to construct the virtual environments in Minecraft. This effect – like an involuntary visual overlay to his surroundings – can last for an hour or so, he says. "It's why I tend to stay away from VR games now – because I still feel fully immersed for too long after taking the headset off," he says.

It raises questions about whether the games industry should be addressing GTP in some way? Since so many games are played by children and young people, Ortiz de Gortari argues that developers should take more responsibility in addressing the potential impact of GTP on susceptible gamers, possibly through their own research, or at least by acknowledging its effects.

Dines says that he would endorse some kind of warning on games. It may only have relevance for a few gamers but that's no different to the warnings about strobe lighting effects, which could induce epileptic seizures in a small subset of players, for example.

"Game developers intentionally craft their products to give certain experiences – they know their game's power," says Farha. "Players need to appreciate that games have to be used correctly. I know I've played too much at times and it didn't make me feel good."

But Nick Ballou, a postdocoral researcher in video games and mental health at the University of Oxford, expresses concern that overemphasising the dangers of GTP will fuel the moral panic around video games or stoke fears that all games are inherently unhealthy. Ballou is currently in the process of analysing data shared with him by the gaming industry. This data covers five leading video game platforms and his goal is to provide the most nuanced picture to date of how games affect people, both for better or worse. He aims to publish the first research from this project this spring. 

Most gamers don't find that their hobby impacts their mental health negatively, he says. Rather, they more commonly report that gaming induces feelings of relief or relaxation, and that it gives them access to communities or offers a sense of achievement and identity. "Any problems are at the extremes [of gaming]," says Ballou. "[Similarly], in small doses, GTP doesn't strike me as particularly problematic. If it was endemic we'd see more people out there behaving in very strange ways. But we don't."

For Ortiz de Gortari, however, there's a lot still to uncover about this extraordinary phenomenon. We still know relatively little about the way gamers unconsciously process what they see and hear during play. A better understanding of this, through a complex and expensive brain scan study, might, she says, help us unravel what happens as GTP kicks in. 

"We have enough evidence that GTP is happening," she says. "Now we need to know more about how and why."