tetris eyes
This past spring I had to uninstall Dots on my phone because it was devastating my battery life and my pride.

It's a ludicrously simple game. The objective is to make as many squares as you can in a minute by connecting like-colored dots on a grid. I got really good at it. So good I was ashamed. If I noticed a person on the subway looking over my shoulder as I played Dots, I would tone down my fiendish thumbwork, purposely throw the game, pretend to be bored, open The New Yorker app, stare at the words and think about Dots. At night, when I was in that weird state between wakefulness and sleep, I would see pastel-colored dots falling into place on the back of my eyelids. I could feel the movement of making a square, and the satisfying little vibration each time one was complete. I couldn't control it, and it made me feel a little crazy. So, I put the question to my friends.

Did they feel lingering effects from video games, too?
"I tried moving people out of my way after a StarCraft bender."
- Dale

"Does seeing the whole world scroll after a Guitar Hero binge count?"
- Taylor

"Both my husband and I think about Candy Crush combos if we've been playing a lot. Like, I remember having a dream about getting two sparkle candies (the ones from 5 in a row) next to each other because...WOW."
- Jane

"First time was on my Gameboy, hearing sounds of a Pokemon appearing in the wild with my eyes closed."
- Jin

"Driving past fields of wheat, wanting to harvest that shit with a tap of the finger."
- Brigid
Some of my friends already knew what I was getting at: "Are you talking about the Tetris effect?" The symptoms they described might be lumped under that term. Some people credit Neil Gaiman with first describing the Tetris effect in a 1987 poem "Virus in digital dreams," but the expression is usually traced back to a 1994 Wired article, in which the author, Jeffrey Goldsmith, details a Tetris bender on his Gameboy in Tokyo: "At night, geometric shapes fell in the darkness as I lay on loaned tatami floor space. Days, I sat on a lavender suede sofa and played Tetris furiously. During rare jaunts from the house, I visually fit cars and trees and people together."

Images on repeat

Over the last two decades, the Tetris effect has worked its way into gaming vernacular, but considering how many people play video games, it may be surprising how little the phenomenon has been studied.

"The Tetris effect is actually not well covered in scientific research," said Karolien Poels, a researcher at the University of Antwerp. "It was in the popular media and a lot of people recognized it but there were just a couple of studies mentioning it."

Perhaps the most famous example is a 2000 study by Harvard psychiatrist Robert Stickgold. He wanted to know why, after a day of mountain climbing, he kept having the sensation of feeling rocks under his hand when he was falling asleep at night, even when he tried thinking about something else. As Stickgold told Australia's ABC News in an interview, this made him think there must be something going on in the brain that is producing these intrusive images. To study the phenomenon in a lab, he turned to Tetris.

He found that students who were made to play Tetris reported, quite consistently, that they saw Tetris pieces floating down in front of their eyes as they were going to sleep. Stickgold also included five amnesiacs in the experiment who could play Tetris just fine, but due to a specific brain damage, couldn't later recall playing it. But they, too, said that they saw blocks floating or turning on their side—even though they couldn't explain the origin of those shapes. One patient, for example, reported seeing "images that are turned on their side. I don't know what they are from. I wish I could remember, but they are like blocks."

This result helped narrow down the underlying mechanism behind the Tetris effect. The brain has two main memory systems: the hippocampus deep in the brain registers the explicit memories of actual life events, or episodic memories, while the cortex holds onto implicit memories—the stuff we learn but don't necessarily have conscious access to. The amnesiacs had damage to their hippocampus, so their Tetris dreaming suggested the effect doesn't rely on the explicit memory system, and that unbeknownst to the patients, their brains were still extracting critical information from the day's events.

Games leaking into life

The brain goes through a nightly rehearsal of what it has learned during the day to consolidate the memories and keep the useful ones. It may be that the Tetris effect is a manifestation of this process. But it describes only one of the diverse experiences people have after spending hours playing a game.
"In the mid-2000s during the Sudoku craze I would think of the streets as vertical or horizontal numerical puzzles I had to solve as I walked."
- Robyn
These experiences, in fact, are not limited to just the nighttime. A major problem with the "Tetris effect" as a term is that it excludes the altered perceptions that get triggered when gamers associate real-life stimuli with video game elements, says Angelica Ortiz de Gortari, a psychologist at Nottingham Trent University. She prefers the expression "game transfer phenomena." In her attempt to define this term over the last five years, Ortiz de Gortari has encountered not just Tetris players who see falling blocks late at night, but also World of Warcraft gamers who have reported seeing health bars above their opponents' heads when playing a real-life game of football and people who have seen the road turn into a moving fret board while driving after a Rock Band binge.

Through several studies and surveys of gamers, Ortiz de Gortari found that game transfer phenomena can happen any time, but they most often occur when people have just finished playing, or when they are in passive states like trying to fall asleep; engaged in trance-life activities like watching TV or driving; daydreaming; or doing an automatic activity like walking or exercising. And these phenomena cover a wide variety of sensory experiences, from hallucinatory noises like lasers, commands and whispers, to bodily sensations, such as the feeling of climbing or flying.

Ortiz de Gortari has also found remarkable similarities among the experiences of gamers who played the same games, suggesting that a video game's structure will largely determine the game transfer phenomena. For example, puzzle games like Tetris and Candy Crush will produce much different effects than massively multiplayer online role-playing games (MMORPGs) like World of Warcraft, and other researchers like Poels have started to investigate those differences.

"MMORPGs are interesting because you need to invest a lot of time in those games otherwise you cannot be fully engaged," Poels said. "We wanted to test whether Tetris effect-like things happen in those games, and we thought they would be richer than those falling blocks you see."
"When I watch football on TV after playing Madden I have the urge to control the players."
- Ryan
Last year, Poels and her colleagues published a study in New Media and Society showing that for habitual World of Warcraft players, elements from the game colored how they perceived physical objects and sounds in the real world. For example, one subject said the signs around his campus immediately called to mind the signposts pointing the way to Stormwind and Ironforge. The game also seeped into their vocabulary—it's not uncommon to hear gamers say they're going on a "fetch quest" to find food, for example. These effects became stronger as the gamers spent more time playing.
"Because of playing way too much Metal Gear Solid V, every time I see a helicopter in Los Angeles (which is often), I have a sudden urge to dive into the pavement and crawl into the nearest bush."
- Sandy
"This study shed a light on what is going on but was not in-depth enough to cover the underlying processes and what is really going on" Poels said. "If we could do more experimental research, we could keep certain conditions under control and we could see which kinds of activities have the most effect on perceptions."

For example, she says it might be interesting to test whether age and years of play changes how gamers experience these after-effects. The brain is known to be adaptable, or "plastic," even in adulthood. A few years ago, scientists showed that the grueling work of memorizing London's web of streets actually changed brain structure of the city's taxi drivers; they gained a greater volume of nerve cells in their hippocampus. Does 10 years of wandering in the infinite landscape of Minecraft grow the hippocampus in the same way? Scientists haven't yet put gamers inside (expensive) MRI machines to find out.

Though game transfer phenomena seem to be quite common experiences, you might be convinced it's a sign of gaming addiction if you saw a PSA recently issued by South Korea's Ministry of Health and Welfare. In the video, distressed gamers who can't remove themselves from the world of a video game hear intrusive sounds, tap their fingers like they're still playing and attack old ladies they perceive as virtual enemies.

These symptoms look a whole lot like game transfer phenomena. However, as Ortiz de Gortari stressed in a blog post, there's still no gold standard for diagnosing gaming addiction. While in some cases, these effects might arise from a legitimate addiction, she generally considers these sensations to be on a spectrum between normal and pathological phenomena. Strangely enough, that might be what makes the Tetris effect and its ilk tough to study: they might just be too mundane to attract funding.

"As an academic researcher, you're more likely to get funding if you link video games to something positive, or most probably, something negative," Poels said (If you couldn't have guessed it, there are dozens, if not hundreds, of studies on the topic of violent video games and aggressive behavior.) "I don't know whether these effects are positive or negative. It's just something that happens. But it's important to study because it could have links to things that people do every day, and if we know how it happens, we can maybe exploit it in some way."