Update, April 13: This article originally included the story of Phineas Gage, a historically famous patient who suffered orbitofrontal cortex damage after an iron rod punctured his skull, inaccurately asserting that Gage experienced distorted time perception after his injury. We regret the error.
For her masters and doctoral research, Heather Berlin set out to answer the question: How accurate is humans’ time perception? Can people reliably tell, without the help of a clock, how many seconds have passed?
To test that, Berlin distracted people by having them read aloud a sequence of numbers printed on cards—this was to keep them from counting in their heads to see how much time had gone by. Participants were told to stop her when they believed 90 seconds had passed.
Berlin spoke to healthy people and people with orbitofrontal cortex lesions in Oxford and London and subjected them all to her time-perception test, to see if the brain injury made a difference. What she found was surprising: Healthy brains actually see time more inaccurately. Participants with undamaged brains tended to let a few more than 90 seconds pass before stopping her, indicating a slightly slower perception of time. Participants with orbitofrontal cortex damage, however, would stop her at almost exactly 90 seconds, indicating a more accurate perception of time.
Being accurate isn’t necessarily a good thing, it turns out. An accurate perception of time can be evolutionarily disadvantageous. One reason why people with healthy brains might perceive time as slightly slower than it actually is (and therefore wait until 95 or 100 seconds have passed before saying 90 seconds have passed) may come down to a neurotransmitter called neuropeptide-Y (NPY).
Charles A. Morgan at the Yale School of Medicine conducted a study four years before Berlin’s findings, where he tested the amount of NPY present in the brains of U.S. Army soldiers. He assessed soldiers prior to training to establish a “control” group, then tested soldiers after a high-pressure, 24-hour survival training, or after what he termed a “P.O.W. experience,” in which soldiers were interrogated, for training, in a tense, realistic prisoner of war situation. This gave him a “stressed” group to work with.
When people with normal brains are stressed, adrenaline is released. The brain is readying the person to attack or to run, according to David Eagleman’s research at Baylor College of Medicine’s Laboratory for Perception and Action. If the situation is sufficiently stressful, then the responses of alarm and fear could become so intense that, without the counteracting release of NPY, they would debilitate the prefrontal cortex, which affects rationality and decision-making, according to Morgan. Fortunately, the release of NPY helps to regulate stress, Morgan says. He found that soldiers who had just undergone survival training or the mock interrogation—the “stressful” group—had significantly greater levels of NPY compared to his control group of soldiers who had not been submitted to these situations. He added that it is not military training that produces these NPY differences but that anyone put in a stressful situation would show higher levels of NPY. Without NPY it would be extremely difficult for people to maintain cognitive skills, motor skills, and decision-making abilities when faced with danger.
As Berlin’s experiment showed, people with healthy brains experience time slightly slower than it is actually is not just in dangerous situations but in normal situations as well. According to Morgan’s research, this might happen because NPY is always being released, just at lower levels during safe situations. So for healthy people, time always seems a little slow, with the potential to slow down even more in the face of danger. This function of stress regulation in the brains of healthy people means that they are able to remain calmer and act more reasonably, in danger and the rest of the time, Morgan says.
Using a test similar to the famous marshmallow experiment (using £80 as the reward rather than a marshmallow), Berlin demonstrated that people with orbitofrontal cortex damage tend to be more impulsive than healthy people because they don’t think they have as much time to make a decision, due to faster time perception. Maybe NPY is less effective on them, due to the brain damage.
People with orbitofrontal cortex “respond rapidly to rewards and [punishments] without assessing the consequences sufficiently,” Berlin writes.
So one’s perception of time seems to affect one’s ability to stay calm, to assess a situation, and to make good decisions. As time slows down, these abilities are strengthened. When the orbitofrontal cortex is damaged, Berlin and Morgan’s findings show that this might very well lead to greater stress and a faster perception of time. But neurology is just one piece of the puzzle. Part of the mystery of inaccurate time perception can also be illuminated by psychology.
* * *
In 2009, Aaron Sackett from the University of Chicago conducted an experiment to test whether people’s expectations could affect how they perceived time. He gave 37 American undergraduate students a selection of text and asked them to underline each word that had a double-letter combination (for example: “This is an epigrammatic riddle.”) Sackett’s research assistant, Rachel Auer, told the participants that the test would last 10 minutes, then made a show of starting her stopwatch and walking out of the room.
Auer conducted two versions of the experiment, each with two variations. In the first version, she varied the amount of time participants were given before she walked back into the room. For one set of participants, time was artificially sped up; they were given only five minutes to take the test before Auer walked back in saying 10 minutes had passed. For the other set of students, time was slowed down; they were actually given 20 minutes, but still told that 10 minutes had passed.
In the second version of the experiment, Auer held the amount of time constant, but varied how much time she told them had passed. Both sets of participants were given 10 minutes to take the test, but one set was told that only five minutes had passed, while the other set was told they’d been given 20 minutes.
After each experiment, the participants were asked to rate how engaging, enjoyable, and challenging they found their task. Both sets of participants for whom time had been “sped up”–that is, the set that were given only five minutes, and the set that were told only five minutes had passed–rated their task as significantly more enjoyable than the other set.
Sackett therefore concluded in his paper and in our conversations that simply being told that time is moving quickly might affect the brain’s perception of time as well. So external cues could also play a role in how quickly or slowly people feel time to be passing.
“If you set the expectation [of a certain amount of time having passed] and then their experience doesn’t fulfill that expectation, it’s quite possible that they would engage in this process of misperceiving time,” Sackett says.
So distorted time perception could be as simple as expecting time to pass in a certain way and then finding that it did not.
In another of Sackett’s experiments, he had students watch a movie in a dark room. He set up the start times so the movie would start and end at three different times, each with its own shift in light. “We set up the show times so that the movie either (a) started and ended before dark, (b) started before dark and ended after dark, or (c) started and ended after dark.” He found that the students who started finished watching the movie while it was still light out reported the strongest time distortion. “You can almost imagine them standing there, blinking in the bright sun, and feeling like the past 90 minutes had been compressed into just a short moment.”
Expectation of time, Sackett says, is time perception. Maybe expectations are set externally, by the appearance of the sun or a researcher telling you “10 minutes have passed.” But without an obvious outside influence, when clocks have been taken away and you’re left with just your brain—if it’s a healthy brain, your expectation will be a little slower than the truth.