May 2010


Perceived Self-Motion is Correlated with Mental Time Travel

If you have an imagination, you don't have to be the protagonist in H. G. Wells' The Time Machine to travel through time. If you've ever eagerly awaited (or painfully dreaded) an upcoming birthday, recalled winning the lottery (don't you wish), or fantasized about eating lunch while listening to your teacher drone on about why the river in the novel symbolizes the birth of modern civilization, you've mentally traveled through time.

Mental time travel is what got me through some of my postdoctoral days; watching spots (proteins) move across a computer screen was usually less than riveting. Besides alleviating boredom, the ability to use past experience (retrospection) to predict future scenarios (prospection) is extremely useful; you'll be far more careful about when and where you leave your bicycle outside if it gets stolen.

Interestingly, very little is known about what affects mental time travel, other than how it can be damaged, e.g. in response to disease. Some scientists have speculated that mental time travel is tied in with the regulation and perception of physical movement, but this hypothesis remains to be thoroughly tested.

Lynden Miles (University of Aberdeen, United Kingdom) and coworkers have recently shown that recalling the future (past) is correlated with forward (backward) physical movement. Here, they demonstrate the reverse relationship, i.e. that the perception of forward (reverse) movement is correlated with people mentally moving forward (backward) in time, adding to research on the possible relationship between time, space, and cognition.

Testing perceived motion and time travel.

The scientists tested the hypothesis that perceived self-motion (vection) would lead people's mind to wander in the direction of the perceived physical motion, i.e. the future for forward motion and the past for backward motion. They studied 26 undergraduates (mostly female) at the University of Aberdeen, who were given course credit for participation in these experiments.

The scientists wanted the students' minds to wander (unprompted) while perceiving themselves to be physically moving forward or backward. They therefore assigned the students an easy task: viewing a simulated star field, moving forward or backward.

The students were instructed to quickly click a mouse button whenever an O (target) appeared on the screen, and to not click when an X (distracter) appeared. One of these two appeared every three seconds, but only 5% of them were targets, i.e. the targets were rare.

By giving the students a dull task to perform, the scientists hoped that the students would spontaneously daydream during the experiment. After the clicking test, the students were all asked whether they were thinking of the future and/or the past (unrelated to the star viewing exercise), discounting all thoughts involving the present, over the course of the experiment.

Remember that some students' star fields were moving forwards, and some were moving backwards. The purpose of these experiments was to test the possible relationship between the direction of simulated motion (forward or backward) and the direction of mental time travel (future or past).

Forward (backward) vection for future (past) daydreams.

The scientists checked whether any of the students were able to figure out the hypothesis that the scientists were testing. None of them were, removing a possible source of bias from the results.

Regarding the students who viewed stars moving backwards, sixty-three percent of (undiscarded) daydreams were of the past. Regarding the students who viewed stars moving forward, sixty percent of (undiscarded) daydreams were of the future.

It's clear that the perception of forward movement is correlated with daydreaming of the future, and perception of backward movement is correlated with daydreaming of the past. This research is therefore highly suggestive of another link between perceived motion and the direction of mental time travel.

This research does not prove that perceived motion directly influences mental time travel. There could be an intermediary between the two, such as a conscious thought of moving forward that in turn leads to daydreaming of the future.

Future research.

Is this relationship between perceived physical travel and mental time travel fundamentally wired into the brain, or is it a cultural phenomenon? The scientists note an interesting case of a particular group of Andeans who speak the Aymara language.

These speakers, in both verbal and nonverbal communication, link the past with the forward direction, and the future with the backward direction. More in-depth research is needed to test the hardwiring and cultural hypotheses of the link between physical travel and mental time travel.

Additionally, further experiments wherein actual physical movement (i.e. not simply perceived movement) is involved may yield a stronger relationship between physical motion and mental time travel than what was reported in this study. Ultimately, studies such as these will be helpful for understanding how different neural processes are linked together, which may help treat (and understand) injuries or disorders wherein some aspect of cognition, sensation, or perception is damaged. for more information:
Miles, L. K., Karpinska, K., Lumsden, J., & Macrae, C. N. (2010). The Meandering Mind: Vection and Mental Time Travel PLoS ONE, 5 (5) DOI: 10.1371/journal.pone.0010825