Keith Makse can tell when a player is getting scared while playing his video game.

The developer behind “Bring to Light,” a horror video game that drops a player into a subway system filled with lurking creatures, Makse designed the game to take in readings from a player’s heartbeat and incorporate that data to make the experience as scary as possible.

“Nothing makes your heart race faster than [hearing] a racing heartbeat,” Makse said. “If you are wearing the heart-rate monitor sometimes you can hear the heartbeat... and it’s your own heartbeat that you hear.”

“Bring to Light” is one of only a few video games in the industry that uses biometrics, in which the physical responses of a player’s body alters their in-game experience — and improves the game for other players as well.

Makse’s system reads a player’s heart rate monitor to change their experience and amplify the terror they feel in real time. If their heart rate indicates their experience could be heightened by more fear, the game’s system might amp up the terror by introducing new scares.

Makse and his team at the Canadian game development studio Red Meat Games released their new indiegame in July (on Friday the 13th, naturally). To escape the terrifying reality, gamers have to use light to solve treacherous puzzles and evade creatures that can sense their terror.

“Horror is designed to allow humans to experience the sensation of fear without actually putting themselves in any physical danger,” Makse said. “This is a safe way of getting in touch with those emotions.”

Had an amazing time at #CGXOttawa last weekend meeting some fabulous folk and sharing in some good ol' scares! #indiegame #indiedev #expo pic.twitter.com/ikUu6SKtJS — Bring to Light (@btl_game) June 29, 2018

Using biometrics in video games was first explored in the early 2000s with some experimentation of human-computer interaction from academics and psychologists. Among the earliest attempts to introduce biometrics into a commercial video game came in 2015, when Erin Reynolds launched “Nevermind,” an indie horror game that used heart-rate monitors and other emotion-detecting technology to measure gamers’ experiences.

While horror games are a relatively small niche in the broader industry, there is optimism that biometrics can help create video games that can offer a certain amount of psychological benefit. Reynolds called her game “a stress management tool disguised as a video game” that aimed to help players recognize and conquer their anxieties.

“For the first time, you have a two way conversation between a person and a video game” Reynolds said.

In each level in “Nevermind,”players assume the minds of trauma victims. They are forced to live through characters’ vividly horrifying experiences, facing psychological trauma or post-traumatic stress. Players must remain calm as they confront progressively scarier scenes.

The biometrics in “Nevermind” were originally only measured through a heart rate monitor and had an emotional component via technology that looked for micro-facial expressions as evidence of anxiety and stress. If the data indicated gamers’ were experiencing increasing stress, the game would introduce a new obstacle or added layers of difficulty.

Nevermind The Flying Mollusk

Another game called “Mindlight” was created for children with anxiety and uses a headset that can read a player’s brainwaves. Players must remain calm to proceed in the game.

The technology behind biometric gaming has its limitations. Graham McAllister, founder of Player Research, a video game design research studio based in the U.K., has studied gamers’ experiences through the lens of biometrics and said there are a number of reasons why biometric games have yet to see mainstream success.

“One is that biometric feedback does not work reliably for everyone,” McAllister said. “This was the reason cited by Nintendo for not releasing their Vitality Sensor.”

Nintendo’s Vitality Sensor was among the most mainstream efforts to bring biometrics to a large audience of gamers. Nintendo introduced the pulse-sensing Wii peripheral at its E3 2009 stage show, but when questioned by an analyst in 2013, the company’s celebrated president, Satoru Iwata, said Nintendo could not launch the project because the technology could not be rendered applicable to every individual person.

McAllister also said that while these tools can accurately measure some physiological measures like heart rate and skin response, he wouldn’t call the technology “a strong indicator of emotions.”

“It is not a linear mapping between these physiological measures and player emotions,” McAllister said. “You still need to use other methods to assess the player’s emotional state, else this leads to guesswork.”

Nevermind The Flying Mollusk

Reynolds, however, believes that biometrics aren’t particularly hard for video game designers to incorporate. She said that as more designers become aware of the technological capabilities, the more games will begin to read their users.

“There really isn’t a technological excuse for why this hasn’t taken off,” Reynolds said. “But I think one reason is that people don’t actually realize all the ways this technology can be used. It’s not really a lack of imagination. It’s more a lack of awareness.”

Biometric gaming opens the door to a variety of ethical questions, with privacy among the most pressing. Both Makse and Reynolds confirmed that all of a player’s personal data collected and interpreted during gameplay is completely anonymized. Their teams recognize that they are dealing with sensitive medical information, so they’re doing their part to ensure that the emerging technology will not be misused.

Reynolds believes the collision of biofeedback and gaming brings the potential to drastically innovate the industry, “but there’s always potential for a dark side too,” she said.

“And the dark side could stop it short in its tracks.”