The brain updates the information that comes from the eyes every 15 seconds so that we can manage daily life without falling into hallucinations. It is like a time machine that provides us with visual stability.
The brain does not present us in real time the images of the world that our eyes capture, but instead updates perceptions every 15 seconds, according to new research from UC Berkeley.
“Our brain is like a time machine. It always takes us back a moment in time. It is as if we had an application that consolidates our visual input every 15 seconds so that we can manage everyday life”, explains one of the authors of the study, Mauro Manassi, in a statement.
“If our brains were always updating in real time, the world would be a jumpy place, with constant fluctuations of shadows, light and movement, and we would feel like we were hallucinating all the time,” adds David Whitney, another of the authors.
The results of this research, published in the journal Science Advances, add to a growing body of research on the mechanism behind the “continuity field,” a function of visual perception by which our brain fuses what we see from steadily to give us a sense of visual stability.
For the study, Manassi and Whitney looked at the perceived mechanism behind the change blindnesswhich occurs when a change is introduced in a visual stimulus and the observer does not notice it.
experiment with faces
They recruited about 100 participants through the platform of crowdsourcing from Amazon Mechanical Turk and asked them to see close-ups of faces transforming from young to old. The faces appeared in video that presented their aging with a time lapse of 30 seconds.
The images in the videos did not include the head or facial hair, but only the eyes, eyebrows, nose, mouth, chin and cheeks, so there would be few clues, such as the thinning of the hairline, about the age of the faces.
What the researchers found was that the participants appreciated the aging of the faces presented more slowly than it appeared in the video.
They noticed more slowly the passing of the years in the face presented in the video and they did not assume in real time the most current image in their aging process.
Perception based on the past
This means that our visual perception is based on the past, and not on the present, because our brain does not update the image we are receiving in real time.
“You could say our brain is procrastinating,” Whitney said. “It’s too much work to constantly update the images, so you stick to the past because the past is a good predictor of the present. We recycle information from the past because it is faster, more efficient and requires less work.”
In fact, the results suggest that the brain works with a slight delay when processing visual stimuli, something that has both positive and negative implications.
“Delay is great for keeping us from being bombarded by visual information in everyday life, but it can also have life-or-death consequences when surgical precision is needed,” Manassi said.
intentional function of consciousness
“For example, radiologists detect tumors and surgeons must be able to see what is in front of them in real time; if their brains are wired to what they saw less than a minute ago, they might be missing something.”
Overall, though, change blindness reveals how the field of continuity is an intentional function of consciousness and what it means to be human, Whitney said.
“We are not literally blind,” he adds. “It’s just that our visual system’s slowness to update itself can make us blind to immediate changes because it clings to our first impression and pushes us back into the past. Ultimately, however, the continuity field supports our experience of a stable world,” Whitney concludes.
Illusion of visual stability through active perceptual serial dependence. Mauro Manassi et al. Science Advances, 12 Jan 2022, Vol 8, Issue 2. DOI: 10.1126/sciadv.abk2480