Vision scientists discover why humans literally don’t meet face to face

Humans may not always agree on politics, religion, sports, and other matters of debate. But we can at least agree on the location and size of objects in our physical environment. Or can we?

Not according to new UC Berkeley research, recently published in the Proceedings of the Royal Society B: Biological Sciences diary, showing that our ability to determine the exact location and size of things varies from person to person, and even within our own individual field of vision.

“We assume that our perception is a perfect reflection of the physical world around us, but this study shows that each of us has a unique visual fingerprint,” said study lead author Zixuan Wang, a PhD student in psychology at the Berkeley University.

The discovery by Wang and other researchers at the Whitney Laboratory for Perception and Action at the University of Berkeley at Berkeley has ramifications for medical, technology, driving and sports practices, among other fields where precise visual localization is critical.

For example, a driver who makes a small miscalculation about the location of a pedestrian crossing the street can cause a catastrophe. Meanwhile, in sports, an error in visual judgment can generate controversy, if not a fierce championship dispute.

Take, for example, the 2004 US Open quarterfinals, in which tennis icon Serena Williams lost to Jennifer Capriati after a series of questionable line calls. A referee incorrectly annulled a line judge who called a backhand shot by Williams, resulting in an apology from the United States Tennis Association.

“Line judges must decide whether the ball is outside or within the parameters. Even an error as small as half a degree of visual angle, equal to a submillimeter displacement in the judge’s retina, can influence the result of the entire match “said Wang, a tennis fanatic.

The researchers tried to understand if different people see objects in their environment in exactly the same way. For example, when looking at a cup of coffee on a table, can two people agree on its exact position and if its handle is large enough to hold it? The result of a series of experiments suggests no, although there is an advantage.

“We can reach a cup of coffee thousands of times in our lives, and through practice we reach our goal,” said Wang. “That is the behavioral aspect of how we train ourselves to coordinate how we act in relation to what we see.”

How they conducted the study

In the first task to test visual location, study participants pinpointed the location of a circular target on a computer screen. In another experiment that analyzed acuity variations within each person’s field of view, participants saw two separate lines at a minimum distance and determined whether one line was located clockwise or counterclockwise to the other line.

And in an experiment that measured perception of size, participants viewed a series of arches of different lengths and were asked to estimate their lengths. Surprisingly, people perceived that exactly the same arches were larger in some places in the visual field and smaller in other places.

Overall, the results showed remarkable variations in visual performance between the group and even within each individual’s field of vision. The data was mapped to show the perceptual distortion fingerprint of each study participant.

“Although our study might suggest that the source of our visual impairments may originate from our brain, more research is needed to discover the neural basis,” said Wang.

“What is also important,” he added, “is how we adapt to them and how we compensate for our mistakes.”