In Head Trip, PopSci explores the relationship between our brains, our senses, and the strange things that happen in between.
SURE, TIME FLIES flies when you’re having fun. Time also seems to stretch out like an old rubber band when you’re stuck in endless back-to-back Zoom work meetings. The latter is an example of chronostasis, a phenomenon in which time appears to pass more slowly than it actually does. A visual example of chronostasis is the stopped clock illusion, which is induced by shifting one’s gaze abruptly to an old-fashioned ticking clock. This action can result in the clock’s second hand appearing to remain stationary for more than a second.
Kielan Yarrow, reader in psychology at the University of London, explains that the key ingredient in the stopped clock illusion—and chronostasis generally—is a rapid movement of eyes from one object to another. Such movements are called “saccades.” Yarrow explains that they can present problems for our brains.
“Whenever you move your eyes,” he says, “it’s rather like moving the camera on your phone.” If you move your phone quickly enough, he says, “you can get a big motion smear, and the whole world appears to jump position.” During a rapid eye movement, there are gaps in the visual information our eyes receive. Our brains respond by “filling in” those gaps to avoid motion blur.
The stopped clock illusion exposes the limits of this retrospective reconstruction. If the clock ticks during the saccade, we do not “see” this tick taking place, because the brain’s reconstruction is based on what it sees at the end of the saccade—at which point the clock has already ticked. The result is that the second hand can seem to have been stationary when it was actually in motion. But since the visual information of the moving second hand was missing during our rapid gaze shift, the brain predicts its “past” position based on the best information…
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