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Virtual reality warps your sense of time: Psychology research demonstrates unique ‘time compression’ effect of virtual reality

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Virtual reality warps your sense of time: Psychology research demonstrates unique ‘time compression’ effect of virtual reality

Psychology researchers at UC Santa Cruz have found that playing games in virtual reality creates an effect called “time compression,” where time goes by faster than you think. Grayson Mullen, who was a cognitive science undergraduate at the time, worked with Psychology Professor Nicolas Davidenko to design an experiment that tested how virtual reality’s effects on a game player’s sense of time differ from those of conventional monitors. The results are now published in the journal Timing & Time Perception.

Mullen designed a maze game that could be played in both virtual reality and conventional formats, then the research team recruited 41 UC Santa Cruz undergraduate students to test the game. Participants played in both formats, with researchers randomizing which version of the game each student started with. Both versions were essentially the same, but the mazes in each varied slightly so that there was no repetition between formats.

Participants were asked to stop playing the game whenever they felt like five minutes had passed. Since there were no clocks available, each person had to make this estimate based on their own perception of the passage of time.

Prior studies of time perception in virtual reality have often asked participants about their experiences after the fact, but in this experiment, the research team wanted to integrate a time-keeping task into the virtual reality experience in order to capture what was happening in the moment. Researchers recorded the actual amount of time that had passed when each participant stopped playing the game, and this revealed a gap between participants’ perception of time and the reality.

The study found that participants who played the virtual reality version of the game first played for an average of 72.6 seconds longer before feeling that five minutes had passed than students who started on a conventional monitor. In other words, students played for 28.5 percent more time than they realized in virtual reality, compared to conventional formats.

This time compression effect was observed only among participants who played the game in virtual reality first. The paper concluded this was because participants based their judgement of time in the second round on whatever initial time estimates they made during the first round, regardless of format. But if the time compression observed in the first round is translatable to other types of virtual reality experiences and longer time intervals, it could be a big step forward in understanding how this effect works.


While there are many informal descriptions of time compression in virtual reality from people who have experienced it first-hand, it’s still an active area of research. One particularly well-known prior study applied virtual reality time compression to shorten the perceived duration of treatment for chemotherapy patients, but that experiment didn’t compare virtual reality with conventional screen formats.

“This is the first time we can really isolate that it’s not just that you’re playing a video game, or the content of whatever you’re seeing,” Mullen said. “It’s really the fact that it is virtual reality versus a conventional screen that contributes to this time compression effect.”

Time compression could be useful in some situations — like enduring an unpleasant medical treatment or passing the time on a long flight — but in other circumstances, it could have harmful consequences.

“As virtual reality headsets get more comfortable to wear for longer periods of time, and as more immersive games are made for this format, I think it would be good to avoid having it become like a virtual casino, where you end up playing more because you don’t realize how much time you’re spending,” Mullen said.

Research on game addiction shows that losing track of time during gameplay can negatively affect a player’s sleep cycle and mood. These effects could be more pronounced in virtual reality, but Mullen says game designers can help to minimize the risk, perhaps by integrating a clock that would appear at regular intervals during gameplay.

It will also be important to discover why virtual reality seems to contribute to time compression. In the paper, Mullen describes one possibility, which relates to the fact that, in virtual reality, a player has less body awareness. Psychology Professor Nicolas Davidenko, a coauthor and advisor on the paper, explained why this might be important.

“In virtual reality, when you look down, you might see nothing where your body normally would be, or you might see a schematic of a body, but it won’t feel like your body,” Davidenko said. “There are theories that we may rely on our heartbeat and other bodily rhythms to help our brain track the passage of time, so if you have a less vivid sense of your body in virtual reality, you might be missing the pulses of this timekeeping mechanism.”

Future experiments to test this theory could yield new insights to help designers maximize benefits and minimize harm from time compression as virtual reality technology continues to grow.

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Artificial reef designed by MIT engineers could protect marine life, reduce storm damage

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The beautiful, gnarled, nooked-and-crannied reefs that surround tropical islands serve as a marine refuge and natural buffer against stormy seas. But as the effects of climate change bleach and break down coral reefs around the world, and extreme weather events become more common, coastal communities are left increasingly vulnerable to frequent flooding and erosion.

An MIT team is now hoping to fortify coastlines with “architected” reefs — sustainable, offshore structures engineered to mimic the wave-buffering effects of natural reefs while also providing pockets for fish and other marine life.

The team’s reef design centers on a cylindrical structure surrounded by four rudder-like slats. The engineers found that when this structure stands up against a wave, it efficiently breaks the wave into turbulent jets that ultimately dissipate most of the wave’s total energy. The team has calculated that the new design could reduce as much wave energy as existing artificial reefs, using 10 times less material.

The researchers plan to fabricate each cylindrical structure from sustainable cement, which they would mold in a pattern of “voxels” that could be automatically assembled, and would provide pockets for fish to explore and other marine life to settle in. The cylinders could be connected to form a long, semipermeable wall, which the engineers could erect along a coastline, about half a mile from shore. Based on the team’s initial experiments with lab-scale prototypes, the architected reef could reduce the energy of incoming waves by more than 95 percent.

“This would be like a long wave-breaker,” says Michael Triantafyllou, the Henry L. and Grace Doherty Professor in Ocean Science and Engineering in the Department of Mechanical Engineering. “If waves are 6 meters high coming toward this reef structure, they would be ultimately less than a meter high on the other side. So, this kills the impact of the waves, which could prevent erosion and flooding.”

Details of the architected reef design are reported today in a study appearing in the open-access journal PNAS Nexus. Triantafyllou’s MIT co-authors are Edvard Ronglan SM ’23; graduate students Alfonso Parra Rubio, Jose del Auila Ferrandis, and Erik Strand; research scientists Patricia Maria Stathatou and Carolina Bastidas; and Professor Neil Gershenfeld, director of the Center for Bits and Atoms; along with Alexis Oliveira Da Silva at the Polytechnic Institute of Paris, Dixia Fan of Westlake University, and Jeffrey Gair Jr. of Scinetics, Inc.

Leveraging turbulence

Some regions have already erected artificial reefs to protect their coastlines from encroaching storms. These structures are typically sunken ships, retired oil and gas platforms, and even assembled configurations of concrete, metal, tires, and stones. However, there’s variability in the types of artificial reefs that are currently in place, and no standard for engineering such structures. What’s more, the designs that are deployed tend to have a low wave dissipation per unit volume of material used. That is, it takes a huge amount of material to break enough wave energy to adequately protect coastal communities.

The MIT team instead looked for ways to engineer an artificial reef that would efficiently dissipate wave energy with less material, while also providing a refuge for fish living along any vulnerable coast.

“Remember, natural coral reefs are only found in tropical waters,” says Triantafyllou, who is director of the MIT Sea Grant. “We cannot have these reefs, for instance, in Massachusetts. But architected reefs don’t depend on temperature, so they can be placed in any water, to protect more coastal areas.”

The new effort is the result of a collaboration between researchers in MIT Sea Grant, who developed the reef structure’s hydrodynamic design, and researchers at the Center for Bits and Atoms (CBA), who worked to make the structure modular and easy to fabricate on location. The team’s architected reef design grew out of two seemingly unrelated problems. CBA researchers were developing ultralight cellular structures for the aerospace industry, while Sea Grant researchers were assessing the performance of blowout preventers in offshore oil structures — cylindrical valves that are used to seal off oil and gas wells and prevent them from leaking.

The team’s tests showed that the structure’s cylindrical arrangement generated a high amount of drag. In other words, the structure appeared to be especially efficient in dissipating high-force flows of oil and gas. They wondered: Could the same arrangement dissipate another type of flow, in ocean waves?

The researchers began to play with the general structure in simulations of water flow, tweaking its dimensions and adding certain elements to see whether and how waves changed as they crashed against each simulated design. This iterative process ultimately landed on an optimized geometry: a vertical cylinder flanked by four long slats, each attached to the cylinder in a way that leaves space for water to flow through the resulting structure. They found this setup essentially breaks up any incoming wave energy, causing parts of the wave-induced flow to spiral to the sides rather than crashing ahead.

“We’re leveraging this turbulence and these powerful jets to ultimately dissipate wave energy,” Ferrandis says.

Standing up to storms

Once the researchers identified an optimal wave-dissipating structure, they fabricated a laboratory-scale version of an architected reef made from a series of the cylindrical structures, which they 3D-printed from plastic. Each test cylinder measured about 1 foot wide and 4 feet tall. They assembled a number of cylinders, each spaced about a foot apart, to form a fence-like structure, which they then lowered into a wave tank at MIT. They then generated waves of various heights and measured them before and after passing through the architected reef.

“We saw the waves reduce substantially, as the reef destroyed their energy,” Triantafyllou says.

The team has also looked into making the structures more porous, and friendly to fish. They found that, rather than making each structure from a solid slab of plastic, they could use a more affordable and sustainable type of cement.

“We’ve worked with biologists to test the cement we intend to use, and it’s benign to fish, and ready to go,” he adds.

They identified an ideal pattern of “voxels,” or microstructures, that cement could be molded into, in order to fabricate the reefs while creating pockets in which fish could live. This voxel geometry resembles individual egg cartons, stacked end to end, and appears to not affect the structure’s overall wave-dissipating power.

“These voxels still maintain a big drag while allowing fish to move inside,” Ferrandis says.

The team is currently fabricating cement voxel structures and assembling them into a lab-scale architected reef, which they will test under various wave conditions. They envision that the voxel design could be modular, and scalable to any desired size, and easy to transport and install in various offshore locations. “Now we’re simulating actual sea patterns, and testing how these models will perform when we eventually have to deploy them,” says Anjali Sinha, a graduate student at MIT who recently joined the group.

Going forward, the team hopes to work with beach towns in Massachusetts to test the structures on a pilot scale.

“These test structures would not be small,” Triantafyllou emphasizes. “They would be about a mile long, and about 5 meters tall, and would cost something like 6 million dollars per mile. So it’s not cheap. But it could prevent billions of dollars in storm damage. And with climate change, protecting the coasts will become a big issue.”

This work was funded, in part, by the U.S. Defense Advanced Research Projects Agency.



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Persistent hiccups in a far-off galaxy draw astronomers to new black hole behavior

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At the heart of a far-off galaxy, a supermassive black hole appears to have had a case of the hiccups.

Astronomers from MIT, Italy, the Czech Republic, and elsewhere have found that a previously quiet black hole, which sits at the center of a galaxy about 800 million light years away, has suddenly erupted, giving off plumes of gas every 8.5 days before settling back to its normal, quiet state.

The periodic hiccups are a new behavior that has not been observed in black holes until now. The scientists believe the most likely explanation for the outbursts stems from a second, smaller black hole that is zinging around the central, supermassive black hole and slinging material out from the larger black hole’s disk of gas every 8.5 days.

The team’s findings, which will be published in the journal Science Advances, challenge the conventional picture of black hole accretion disks, which scientists had assumed are relatively uniform disks of gas that rotate around a central black hole. The new results suggest that accretion disks may be more varied in their contents, possibly containing other black holes, and even entire stars.

“We thought we knew a lot about black holes, but this is telling us there are a lot more things they can do,” says study author Dheeraj “DJ” Pasham, a research scientist in MIT’s Kavli Institute for Astrophysics and Space Research. “We think there will be many more systems like this, and we just need to take more data to find them.”

The study’s MIT co-authors include postdoc Peter Kosec, graduate student Megan Masterson, Associate Professor Erin Kara, Principal Research Scientist Ronald Remillard, and former research scientist Michael Fausnaugh, along with collaborators from multiple institutions, including the Tor Vergata University of Rome, the Astronomical Institute of the Czech Academy of Sciences, and Masaryk University in the Czech Republic.

“Use it or lose it”

The team’s findings grew out of an automated detection by ASAS-SN (the All Sky Automated Survey for SuperNovae), a network of 20 robotic telescopes situated in various locations across the northern and southern hemispheres. The telescopes automatically survey the entire sky once a day for signs of supernovae and other transient phenomena.

In December of 2020, the survey spotted a burst of light in a galaxy about 800 million light years away. That particular part of the sky had been relatively quiet and dark until the telescopes’ detection, when the galaxy suddenly brightened by a factor of 1,000. Pasham, who happened to see the detection reported in a community alert, chose to focus in on the flare with NASA’s NICER (the Neutron star Interior Composition Explorer), an X-ray telescope aboard the International Space Station that continuously monitors the sky for X-ray bursts that could signal activity from neutron stars, black holes, and other extreme gravitational phenomena. The timing was fortuitous, as it was getting toward the end of Pasham’s year-long period during which he had permission to point, or “trigger” the telescope.

“It was either use it or lose it, and it turned out to be my luckiest break,” he says.

He trained NICER to observe the far-off galaxy as it continued to flare. The outburst lasted for about four months before petering out. During that time, NICER took measurements of the galaxy’s X-ray emissions on a daily, high-cadence basis. When Pasham looked closely at the data, he noticed a curious pattern within the four-month flare: subtle dips, in a very narrow band of X-rays, that seemed to reappear every 8.5 days.

It seemed that the galaxy’s burst of energy periodically dipped every 8.5 days. The signal is similar to what astronomers see when an orbiting planet crosses in front of its host star, briefly blocking the star’s light. But no star would be able to block a flare from an entire galaxy.

“I was scratching my head as to what this means because this pattern doesn’t fit anything that we know about these systems,” Pasham recalls.

Punch it

As he was looking for an explanation to the periodic dips, Pasham came across a recent paper by theoretical physicists in the Czech Republic. The theorists had separately worked out that it would be possible, in theory, for a galaxy’s central supermassive black hole to host a second, much smaller black hole. That smaller black hole could orbit at an angle from its larger companion’s accretion disk.

As the theorists proposed, the secondary would periodically punch through the primary black hole’s disk as it orbits. In the process, it would release a plume of gas , like a bee flying through a cloud of pollen. Powerful magnetic fields, to the north and south of the black hole, could then slingshot the plume up and out of the disk. Each time the smaller black hole punches through the disk, it would eject another plume, in a regular, periodic pattern. If that plume happened to point in the direction of an observing telescope, it might observe the plume as a dip in the galaxy’s overall energy, briefly blocking the disk’s light every so often.

“I was super excited by this theory, and I immediately emailed them to say, ‘I think we’re observing exactly what your theory predicted,'” Pasham says.

He and the Czech scientists teamed up to test the idea, with simulations that incorporated NICER’s observations of the original outburst, and the regular, 8.5-day dips. What they found supports the theory: The observed outburst was likely a signal of a second, smaller black hole, orbiting a central supermassive black hole, and periodically puncturing its disk.

Specifically, the team found that the galaxy was relatively quiet prior to the December 2020 detection. The team estimates the galaxy’s central supermassive black hole is as massive as 50 million suns. Prior to the outburst, the black hole may have had a faint, diffuse accretion disk rotating around it, as a second, smaller black hole, measuring 100 to 10,000 solar masses, was orbiting in relative obscurity.

The researchers suspect that, in December 2020, a third object — likely a nearby star — swung too close to the system and was shredded to pieces by the supermassive black hole’s immense gravity — an event that astronomers know as a “tidal disruption event.” The sudden influx of stellar material momentarily brightened the black hole’s accretion disk as the star’s debris swirled into the black hole. Over four months, the black hole feasted on the stellar debris as the second black hole continued orbiting. As it punched through the disk, it ejected a much larger plume than it normally would, which happened to eject straight out toward NICER’s scope.

The team carried out numerous simulations to test the periodic dips. The most likely explanation, they conclude, is a new kind of David-and-Goliath system — a tiny, intermediate-mass black hole, zipping around a supermassive black hole.

“This is a different beast,” Pasham says. “It doesn’t fit anything that we know about these systems. We’re seeing evidence of objects going in and through the disk, at different angles, which challenges the traditional picture of a simple gaseous disk around black holes. We think there is a huge population of these systems out there.”

“This is a brilliant example of how to use the debris from a disrupted star to illuminate the interior of a galactic nucleus which would otherwise remain dark. It is akin to using fluorescent dye to find a leak in a pipe,” says Richard Saxton, an X-ray astronomer from the European Space Astronomy Centre (ESAC) in Madrid, Spain, who was not involved in the study. “This result shows that very close super-massive black hole binaries could be common in galactic nuclei, which is a very exciting development for future gravitational wave detectors.”

This research was supported in part NASA.



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Robot, can you say ‘cheese’?

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Virtual reality warps your sense of time: Psychology research demonstrates unique ‘time compression’ effect of virtual reality



What would you do if you walked up to a robot with a human-like head and it smiled at you first? You’d likely smile back and perhaps feel the two of you were genuinely interacting. But how does a robot know how to do this? Or a better question, how does it know to get you to smile back?



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