Psychologists Demonstrate Illusion That Could Be Screwing Up Our Perception Of Time

How do you judge when an event occurred in the past? For big things that happened across years, we have calendar reminders; holidays, birthdays, and other events that serve as landmarks for our recollection. But what about on the smaller level? For many of us, our days and weeks are pretty same-y, filled with headlines, deadlines, and to-do lists that blend into a kind of repetitive soup.

Without some sort of reference point, so the general belief goes, people tend to remember based on how strong the memory is. In this way, a vivid memory is deemed more recent, while fainter, fuzzy ones probably occurred further in the past. At the same time, we tend to believe that repeated experiences produce stronger memories, which, given the above assumption, should result in better recall and a sense that they happened more recently. However, the new study demonstrates that this is not always the case; instead, it can lead to what is known as the “temporal repetition effect”, an illusion that repeated experiences happened further into the past than they really did.

In their study, Brynn E. Sherman, soon-to-be Assistant Professor at Ohio State University, and Sami Yousif, an Assistant Professor in the Department of Psychology and Neuroscience, conducted six online experiments using object images and memory tasks to see if repetition of content would result in this distortion of mental timelines.

“We propose a specific factor that powerfully distorts temporal memory: the number of times that information is encoded. Specifically, we suggest that the more times a piece of information is encoded, the further away in time it is remembered as having initially occurred”, they explain in their paper.

“This prediction is born out of subjective experience: If you read a headline on a Monday and then hear it repeated over and over again throughout the week, the initial event may seem further away than another headline seen at the same time that was not incessantly repeated.”

In their first experiment, 50 participants were shown a sequence of images of objects, some of which repeated. They were then asked to recall when they had originally seen each image in the sequence. Each repeated image was paired with an image that was only shown once right before it in the sequence. This provided the researchers with a point for direct comparison. Despite their proximity, participants consistently identified the repeated object as having occurred earlier than the non-repeating one.

It also seems that the more often the image was repeated, the stronger the time distortion became. Images that were repeated five times were remembered as having occurred further back than images that were repeated only three times.

In the second experiment, the team attempted to establish whether the temporal distortions seen in the first experiment were due to what is called an “event boundary”. This is the same memory lapse phenomenon that occurs when you find yourself forgetting why you have walked into a room. This time, participants were shown the images as a continual sequence, rather than in separate blocks of images (as in the first experiment). The results were ultimately the same, even when the objects appeared in a continuous sequence.

The third experiment focused on whether attention would make a difference. In this case, participants were explicitly told that they would be asked to judge when images appeared for the first time. Even with this prior knowledge, participants still reported repeated objects as occurring earlier than they really did. Even when participants were asked to indicate whether they had seen the item before during the viewing phase (the setup for the fourth experiment), the same phenomenon occurred: the more times they saw an image, the more likely they were to say it first appeared earlier in the sequence.

In the fifth experiment, the researchers provided an alternative approach. In this case, participants were only shown two images – one repeating and one that did not – and asked to identify which appeared first. In this experiment, the non-repeating image always came first in the sequence, but the participants consistently identified the repeating image as being first.

In the final experiment, the researchers tested whether the temporal repletion effect occurred not only on the scale of minutes, but of days. They ran a week-long experiment where participants viewed streams of images on five consecutive days. Then, three days later, they were asked to place the items on a timeline, similar to the approach of the first experiment. They were also asked to recall how many times they had seen a given image. As you may have guessed, the same result occurred – participants recalled the repeated image as having occurred earlier than it did.

This suggests the temporal illusion is a feature of longer-term memory as well as a spasm in our short-term recall. It demonstrates that our sense of time can be faulty, and the belief that something happened in the more distant past may not be reliable, especially if it was repeated multiple times.

“Across six experiments, we found robust evidence that participants’ temporal memories are systematically distorted: Repeated information was consistently remembered as having initially occurred earlier in time than information presented only once. This temporal repetition effect is notable not only for its existence, but its magnitude,” Sherman and Yousif write.

According to the authors, the vast majority of academic work on time perception focuses on temporal perception of the present, such as how our perception of duration in the present moment is influenced by surprise or repetition. This study, however, demonstrates that our temporal perception of the past is just as important in our everyday lives.

“[A]lthough we are rarely called upon to ask how long an experience lasted (especially on the scale of seconds), we are constantly called upon to remember when things occurred,” the pair explains.

There are a few reasons why this illusion could occur. One is that repetition acts like a kind of “reminder” which reinforces the memory of its first appearance, embedding it further into our minds. Over time, this can make the initial experience feel like it occurred earlier than it did. Another explanation suggests that our temporal sense is not necessarily based on memory per se, but is rather constructed from cues. If this is so, then the more times something is repeated, the further it is assumed to have occurred in the past.

The researchers note that this sense of time is important in several ways that are personal to us and our sense of self, emotion, and motivation. The feeling that something happened “only yesterday” makes us feel like it is more significant, while the idea that something happened further in the past can contribute to nostalgia.

“Perhaps perceived temporal distance from an event also influences how we understand it,” they write.

“Perceiving the COVID lockdowns as occurring long ago may cause us to imagine it less concretely; maybe the distance from it prevents us from feeling the need to prepare for the next pandemic. In this way, when we remember something may sometimes be almost as important as what we remember about it. Through this lens, it may be surprising that our sense of time is subject to remarkable, predictable illusion.”

The paper is published in Psychological Science.