Research shows the way we perceive time passing, as either fast or slow, can be shaped by all manner of things, from our heartbeat and catching someone's eye, to the familiarity of a place.
A new study has found that the way images look can also shift our perception of moments passing. What's more, the time someone thinks they spend looking at an image influences their recall of it.
In a series of experiments, researchers from George Mason University in the US asked a total of 170 people to view various images that flashed up on a screen for different durations of less than a second. Upon viewing, participants had to hit a button to indicate whether they thought they had seen the images for a short or long time.
The researchers found that larger scenes and more memorable images tricked the brain into thinking it had viewed images longer than it did, whereas cluttered pictures seem to make time contract.
Though results have been mixed, past research suggests the way images influence time perception could be related to attention somehow, with larger, bolder, brighter images thought to dilate time by attracting our focus.
But those same features could distract the part of our brain that keeps track of time, so it seems to pass faster. The content of images, not just their complexity, might also resonate with some people more than others.
The findings from this latest study do little to resolve those opposing theories. Instead, the researchers incorporated a new factor in the memorability of images, which some evidence suggests is a unique property that hooks our brains in ways independent of attention.
"Do these images last longer because they are more memorable, or are they more memorable because they last longer?" cognitive neuroscientist Alex Ma and colleagues asked in their study.
It turns out both are true, in these lab experiments where some participants were brought back into the lab to view a second collection of images, half of which they had seen the previous day.
Images rated as memorable were perceived to have been viewed longer, and this effect was consistent from trial to trial, while images thought to be longer lasting were also remembered better.
In considering ways to explain these findings, Ma and colleagues suggest that the time dilation effects of memorable images might help the visual system process information, to overcome bottlenecks.
"In this way, time is dilated or compressed to increase the amount of information that can be processed in any given instance," the trio of researchers write in their paper.
To test that idea, they used an artificial neural network to model the ventral visual system, in which images are progressively processed over time.
"We find that more memorable images are processed faster, and that this increase in processing speed predicts both the lengthening and the increased precision of perceived [time] durations," Ma and colleagues report.
But as other research has pointed out, what makes an image memorable could be very personal. Other studies show images we find emotional can distort time which makes sense because the parts of the brain that process time also regulate emotions.
So there's a lot more to understand about how our brain perceives time, and how that varies from person to person. The results make one thing clear though: our body might hum along to the beat of its biological clocks, but the brain's perception of time is anything but steady.
"These findings provide evidence for a link between image features, time perception and memory that can be further explored with models of visual processing," the authors conclude.
The study has been published in Nature Human Behaviour.