Time can feel very different. Sometimes hours fly by, sometimes minutes seem to stretch on forever. A study now shows that our visual perception also shapes our sense of time. If we see a particularly striking image, we have the impression that we have looked at it for longer than we actually did. In comparison, images of uncluttered scenes give us the opposite feeling. A neural network model shows that this effect is likely related to the processing speed in our brain. The results suggest that we do not have a universal “internal clock” but rather judge time subjectively based on external stimuli.
When we read an exciting book or spend an evening with friends, we hardly notice how time passes. With less popular tasks, however, it can happen that after what feels like an hour we look at the clock and realize that only five minutes have passed. Even on very small time scales in the range of seconds, our perception of time can vary depending on external influences. But what exactly influences our sense of time and what mechanisms are behind it?
Clarity influences time perception
A team led by Alex Ma from George Mason University in Virginia investigated these questions through a series of experiments. The researchers showed their test subjects numerous images one after the other, with each image being presented for 0.3 to 0.9 seconds. After each picture, the test subjects were asked to indicate by pressing a button whether they thought they had seen the picture for a long time or for a short time.
The result: When the test subjects saw images of large, clear scenes, such as a concert hall or a football stadium, they often had the impression that they had seen the image for longer than it was actually shown to them. Very confusing images, on the other hand, had the opposite effect. A cluttered room, a busy marketplace and similar images gave the test subjects the feeling that they had only caught a brief glimpse – even if in reality the image had been presented longer than that of a more manageable scene.
Interplay between memorability and perceived duration
In another experiment, the researchers also took into account how memorable the respective images were. To do this, they used images for which previous studies had already classified how well subjects could later remember them. In order to find out how precisely the test subjects can estimate time, in this experiment they were not simply asked to press “short” or “long”, but rather to hold down a key for exactly as long as they thought they had seen the image. This showed that they were able to estimate the duration of more memorable images more accurately.
However, when it came to less memorable images, they usually underestimated how long they had been looking at them. The other way around, there was also a relationship between perceived duration and memorability: “The longer the perceived duration of an image, the more memorable it is,” reports the team. In a test the following day, test subjects were more likely to remember images that they had the impression that they had seen for a longer period of time the day before.
Accelerated processing
In search of the underlying mechanisms, the researchers created a neural network model of our visual system. In this way, they were able to reconstruct how our brain probably reacts to the images. “We found that more memorable images are processed more quickly and that this increase in processing speed predicts both the lengthening and increased precision of perceived time duration,” the researchers write.
This suggests that our brain does not rely on an independent, internal clock when estimating time, but that external stimuli can influence the processing speed and thus also the perceived time. “These results demonstrate a connection between image features, time perception and memory, which can be further explored using models of visual processing,” say the researchers.
Source: Alex Ma (George Mason University, Fairfax, Virginia, USA) et al, Nature Human Behavior, doi: 10.1038/s41562-024-01863-2