Neurophilosophy

“WHEN a man sits with a pretty girl for an hour,” said Albert Einstein, “it seems like a minute. But let him sit on a hot stove for a minute, and it’s longer than any hour.” Einstein was describing one of the most profound implications of his Theory of General Relativity – that the perception of time is subjective. This is something we all know from experience: time flies when we are enjoying ourselves, but seems to drag on when we are doing something tedious.

The subjective experience of time can also be manipulated experimentally. Visual stimuli which appear to be approaching are perceived to be longer in duration than when viewed as static or moving away. Similarly, participants presented with a stream of otherwise identical stimuli, but including one oddball, or “deviant”, stimulus, tend to perceive the deviant stimulus as lasting longer than the others. The underlying neural mechanisms of this are unknown, but now the first neuroimaging study of this phenomenon implicates the involvement of brain structures which are thought to be required for cognitive control and subjective awareness.

The apparent prolonged duration of a looming or deviant stimulus is referred to as the time dilation illusion, and three possible, but not mutually exclusive, explanations for why it might occur have been put forward. First, the stimulus might be perceived as lasting longer because it has unusual properties which require an increased amount of attention to be devoted to it. Alternatively, the perceived duration of the stimulus might reflect the amount of energy expended in generating its neural representation (that is, duration is a function of coding efficiency). Finally, the effect might be due to the intrinsic dynamic properties of the stimulus, such that the brain estimates time based on the number of changes in an event.

Of particular relevance to the third hypothesis is the observation that looming stimuli are associated with a distorted subjective perception of time, such that their duration is perceived to be longer than it actually is. Marc Wittmann and his colleagues exploited this in their new study. They recruited 20 participants and scanned their brains as they viewing a stream of five visual events. All five stimuli were static and of an identical duration, except for the fourth. This ‘deviant’ target consisted of an expanding or shrinking disc – which mimicked an object moving toward, or away from, the participants, respectively – and whose duration was systematically varied for each trial. The participants were required to judge the duration of the deviant stimulus in comparison to the other four, by answering the question, “Is the target longer or shorter than the other events?”

The time dilation effect was only observed in trials which included looming deviant targets. The looming stimulus, which had a duration 409 milliseconds (ms, thousandths of a second), was reported by the participants to be equivalent to the four static stimuli, which lasted 490 ms. The opposite effect was observed in trials including the receding stimulus. The shrinking discs, which actually lasted 511 ms, were also reported to being of equivalent duration to the static stimuli. The extent of this latter effect was, however, lesser than the time dilation effect – whereas looming stimuli were perceived to last 81 ms (or almost one tenth of a second) longer than they actually were, the duration of the receding stimuli was ‘compressed’ by just 21 ms (just over one fiftieth of a second).

Thus, the participants consistently overestimated the duration of the looming stimulus and underestimated that of the deviant receding stimulus. Analysis of the fMRI data revealed that both types of deviant stimulus produced similar brain activation patterns. When they compared the brain’s response to looming versus static stimuli with its response to receding versus static stimuli, the researchers observed increased activation in a network of areas including the left insula and surrounding areas, the anterior cingulate gyrus, the right middle frontal cortex and the left and right superior frontal regions. Additionally, receding stimuli alone activated the right insula and the entire cingulate gyrus in both hemispheres.

The looming and receding stimuli therefore led to asymmetrical activation in the so-called “core control network“, which is critical for selecting, switching between and attending to prominent features in the environment. Differences between the two activation patterns further revealed the neural correlates of the time dilation effect. The looming stimulus was found to produce stronger activation of the left middle and superior frontal cortex, including the cingulate gyrus, and the posterior cingulate and pre-cuneus. Some of these structures, which are located near the brain’s midline, have been associated with a “default network” which is engaged when the brain is at rest, but whose activity is suspended during any goal-directed action. They are also associated with the processing of self-referential information.

The researchers observed a strong time dilation effect in the looming, but not the receding, condition. They suggest that it is the occurance of a looming stimulus, and not an oddball or deviant stimulus per se, that causes an overestimation of time, but do not rule out that attentional and emotional factors might also be involved. They speculate that the expanding discs – which mimic an approaching object – evoke self-referential processes which act to signal the presence of a potential threat. In such a situation, an illusion of time dilation could facilitate an effective escape. People often report that time seems to slow down during dangerous events, such as a car accident or a robbery, but it remains to be seen whether looming visual stimuli are interpreted as threatening under experimental conditions.

Related:


Wittmann, M., et al (2010). The neural substrates of subjective time dilation Front. Hum. Neurosci. DOI: 10.3389/neuro.09.002.2010.

Eagleman, D. & Pariyadath, V. (2009). Is subjective duration a signature of coding efficiency? Phil. Trans. R. Soc. B. 364: 1841-1851. [PDF]

van Wassenhove V., et al. (2008) Distortions of Subjective Time Perception Within and Across Senses. PLoS ONE 3: e1437. DOI: 10.1371/journal.pone.0001437.

Tse, P.U., et al. (2004). Attention and the subjective expansion of time. Percept. Psychophys. 66: 1171-1189. [PDF]

Comments

  1. #1 Doru
    January 23, 2010

    I found this blog to be very fascinating and thoughtful!
    I make some distinction between the biological and psychological time line perception of the brain, but never thought about the time dilating mechanism to enable fast adaptation in threatening situations.

  2. #2 Lance P
    January 23, 2010

    This must apply to “simulated” threats as well. I remember the first time I played paint ball. When it was announced over the PA “2 minutes down, 8 to go” my brain went “It’s ONLY been 2 MINUTES?!”

    : )

  3. #3 Scientific Chick
    January 23, 2010

    Evolutionarily, it makes more sense to me that a looming threat would seem to be coming faster (or would seem closer), to ensure a sense of urgency and allow for escape. That being said, the three hypotheses you put forward to explain the opposite effect also make perfect sense to me as well.

    Overall, I’m confused. :)

    Thanks for a nice post.

  4. #4 Scilogue
    January 23, 2010

    This is very interesting research. Is there any data to suggest an effect in autonomic nervous system? Perhaps increased activity in the sympathetic nervous system causes time to move more slowly and vice a versa in the parasympathetic system?

    It does make evolutionary sense to extend the perception of time when under threat.

  5. #5 khan
    January 23, 2010

    Totally anecdotal: Many years ago I was almost part of an auto accident. Time did seem to slow down and allow me to avoid crashing.

  6. #6 Michael
    January 23, 2010

    Isn’t a there another possibility? It seems plausible to me that there is no fact of the matter as to how long a certain experience seemed at the time, and the phenomenon of time dilation is about our memory of the events.

  7. #7 Evelyn Wolke
    January 23, 2010

    Anecdotally, I have been in several very hazardous situations while working in an institution for people with multiple disabilities. When I perceived these events as seriously threatening, I often felt my perception of time “slow down” so that I could appreciate the situations in a more complete fashion and react (hopefully) more effectively. In one of these events I was literally thrown across a room (and I have never been a lightweight) and felt quite irked that my reaction time wasn’t fast enough to shield me from the inevitable concussion that was the result of hitting the wall. Oddly, though I recall this, I do not recall a few hours of the time thereafter.

  8. #8 Christopher Ak.
    January 24, 2010

    The subjective experience of time is much more complicated. I expect that you will find many mechanisms in play. It would be interesting to see a study correlating the following with time perception:
    - Level of adrenaline during an incident (or some other measure of the “flight or fight” trigger).
    - “Fun factor”, i.e. subjective rating of how fun the activity was
    - An ‘opposite’ of adrenaline, such as serotonin, dopamine etc.

    Another interesting area, is to look at how people remember events that have long since passed. The more ‘eventful’, fun or frightening an experience is, the more things you can recall about it. I have a theory that we measure time past by the number of incidents our brains have deemed worthy to record. 10 years in a boring job may therefore be equivalent to 1 minute skydiving. This perceived time is what really matters to us.

    I expect that scientists will eventually prove something we have all known for a very very long time: the value of living each moment to the fullest.

  9. #9 Crazy Mermaid
    January 24, 2010

    Having lived through several seriously hazardous events, I can attest to the fact that time does indeed seem to slow down during those events. This explanation is very interesting.

  10. #10 Victor Antonio
    January 25, 2010

    Great article…love the insight!

  11. #11 the heven's
    February 7, 2010

    wow!this page on time dilation has helped me so much THANKS!!!

  12. #12 Troy
    February 7, 2010

    I remember once I was on a date with my crush last year and to me it felt like 10 minutes but actually it was AN HOUR I couldn’t believe it it really is weird how time works:)

  13. #13 per
    April 9, 2010

    hi, I am writing a poem. can I use the sentence “Time is dilating more adaption”, does it make sens? I am norwegian, so thats why I ask :)

    per

  14. #14 Mo
    April 11, 2010

    per: No, that doesn’t make sense. I’m not sure what you’re trying to say, so I can’t make any suggestions.

  15. #15 Paul Wenyans
    April 18, 2010

    There’s a couple of things wrong here. First, this dilation effect you’re talking about isn’t called “time” dilation but “duration” dilation. Time dilation has to do with physics and the physical dilation of time is response to extreme velocities or strong gravitational fields.

    Second, the duration dilation test that you are referring to is by David Eagleman and that test has been debunked as a not even wrong by this paper – http://aet-radal.blogdrive.com/

    The fact that people claim that they have survived serious harm from accidents because their perception of time seemed to slow down is the first hint that the effect is real, otherwise those people would’ve been hurt or killed.

  16. #16 vivek mishra
    August 12, 2010

    Once my leg slipped from a running bus, but to my surprise , it seemed that time had stopped & i was back in the bus in less than i sec. Know i know how it happened.

  17. #17 bactrim discount
    April 18, 2011

    best for you, http://bactrim.freeforums.org/ bactrim, 90464,