We, as humans, have a rather thin grip on the concept of time. We have never realized how tenuous it was until a couple of weeks ago the Foundational Questions Institute organized a conference on the nature of time. How correctly we perceive the past, present, and future?
The meeting was a mash-up of different disciplines: fundamental physics, philosophy, neuroscience, as well as complexity theory. Crossing academic disciplines may be overrated, as the physicist-blogger Sabine Hossenfelder pointed out, but it is fun for sure. There is something exotic about brains. At the meeting, the neuroscientists’ talks were about how our minds perceive the past, present and the future. “Perceive” is probably not a word that is strong enough: our brains construct the past, present, as well as the future, and sometimes get it badly wrong.
The concept of time
Kathleen McDermott, a neuroscientist of Washington University, started by quoting famous memory researcher Endel Tulving, who called our ability to remember the past, as well as to anticipate the future “mental time travel.” The point of Tulving was that we do not use the phrase “time travel” lightly in front of a group of physicists that considered the concept as an inconvenient metaphor but a genuine possibility.
McDermott outlined the case of patient K.C., who has even worse amnesia than the better-known H.M. on whom the film Memento was based. The patient K.C. developed both retrograde, as well as anterograde amnesia when he had a motorcycle crash in 1981. He cannot remember anything that happened more than a few minutes ago. He retains facts, as well as skills, but he cannot remember actually doing anything or being anywhere. Not only he cannot recall the past, but he cannot envision the future. When researchers ask him to picture himself somewhere he wants to go; he says that all he sees is “a big blankness.” Also, another patient that McDermott has worked with can explain the future in the abstract, but he says that he cannot imagine himself in it.
In order to investigate the perception of past, as well as the future in people that do not have brain injuries, McDermott did fMRI brain scans of 21 college students, asking them to recall some specific incident in their past and then envision themselves in a particular future scenario. Even though subjectively the two feel very different, the scans showed the same patterns of activity. Areas spread all over the brain lit up; it disturbs our temporal perception.
As a control, he also asked them to remember events involving Bill Clinton, ones in which they were not personally involved, and the patterns were very different. In a study that followed, McDermott asked 27 students to anticipate an event in both a familiar and an unfamiliar place.
The conclusion is that memory is essential to constructing scenarios for ourselves in the future. Our ability to project forward, as well as recollect the past both develop around the age of 5 and people that are good at remembering also report having vivid thoughts about the future.
Cognitive psychologists have found that sometimes, confidence correlates with accuracy, and sometimes it does not. Henry Roediger, a colleague of McDermott, who studies metacognition –thinking about thinking – gave volunteers a memory word test. They had to remember a list of given words; after that, a series of words were presented to them, and they had to indicate whether each of those words had been on the original list. Moreover, they had to say how confident they felt about their answer.
Roediger said that people did pretty well on the tests, and their confidence scores tracked the accuracy of their recall. Their blind spots were predictable. They systematically messed up, both in recall accuracy and self-assessment, when presented words which were not on the list but were just synonyms of those that were. The findings match what actually occurs with eyewitnesses. We get the things broadly right, but we are easily confused with similar situations, as well as faces.
What about the animals?
For example, the fish generates an electric field of about one millivolt per centimeter at a frequency which ranges from 50 to 2000 Hertz. Water fleas, its prey, give themselves away by disrupting the field.
Though, for land animals, the things are entirely different. They have much bigger sensory volume than their motor volume since light travels much farther in the air than in seawater. So, at the time when our ancestors crawled out of the sea, they won the chance to plan their behavior in advance. The animals which could arbitrage the difference in sensory and motor volumes gained an evolutionary advantage.
The exciting thing about neuroscience is that you can do the experiments on yourself. For instance, David Eagleman of the Baylor College of Medicine proceeded to treat people as his test subjects. Using a few visual illustrations, he demonstrated that we are all living in the past: our consciousness lags 80 milliseconds behind the actual events.
The cohesiveness of consciousness is actually essential to our judgments about cause and effect. Because of that, it is also essential to our sense of self. In one experiment, Eagleman together with his team asked volunteers to press a button to make a light blink – with a slight delay. After 10 or more presses, the people cottoned onto the delay and started to see the blink occurring as soon as they pressed the button. Then, the experimenters reduced the delay, and people reported that the blink occurred before they pressed the button.
In one experiment Eagleman sought to find out why time passes more slowly when we are very scared. Does something really happen in our brain? For example, the time resolution of perceptions seeds up – or do we just think that it is like that?
After brainstorming some scare tactics which would probably not have passed muster with a university ethics committee, he hit upon asking volunteers to take one of those Freefall or Demon Drop rides which you can find in amusement parks.
They wore a special watch that had digits counted up too quickly for people to register them under normal conditions—thinking that, if perception really did speed up, people would have the ability to read the digits.
But, they couldn’t. Even though they consistently reported that the ride took about a third longer than it really did, this must have been some kind of trick of memory; their hyperaccurity was a mirage.
The limits of perception
We build our physics on recognition of the limits of perception. The whole point of theories like the one for relativity is to separate objective features of the world from artifacts of our perspective.
Time can play a lot of roles in physics, from defining casual sequences to giving a direction to the unfolding of the universe. How many of those roles are rooted in the contingent ways our brains perceive time? How might an alien being, that perceives time in a completely different way, formulate physics?
Image Credit: Shutterstock (licensed by IBMN)/By Vlue
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