Vision scientists discover why people literally don't see eye to eye
Study finds visual localization and acuity varies from person to person


Date:
July 14, 2020
Source:
University of California - Berkeley
Summary:
We humans may not always see eye to eye on politics, religion,
sports and other matters of debate. And now it turns out we also
cannot agree on the location and size of objects in our physical
surroundings, according to new research.



FULL STORY ==========================================================================
We humans may not always see eye to eye on politics, religion, sports
and other matters of debate. But at least we can agree on the location
and size of objects in our physical surroundings. Or can we?

==========================================================================
Not according to new research from the University of California,
Berkeley, recently published in the Proceedings of the Royal Society B: Biological Sciences journal, that shows that our ability to pinpoint the
exact location and size of things varies from one person to the next,
and even within our own individual field of vision.

"We assume 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 UC Berkeley doctoral student in psychology.

The discovery by Wang and fellow researchers in UC Berkeley's Whitney Laboratory for Perception and Action has ramifications for the practices
of medicine, technology, driving and sports, among other fields where
accurate visual localization is critical.

For example, a driver who makes even a small miscalculation
about the location of a pedestrian crossing the street can cause a
catastrophe. Meanwhile, in sports, an error of visual judgment can lead
to controversy, if not a fiercely disputed championship loss.

Take, for example, the 2004 U.S. Open quarterfinals, in which tennis icon Serena Williams lost to Jennifer Capriati after a series of questionable
line calls. An umpire incorrectly overruled a line judge who called a
backhand hit by Williams as in, resulting in an apology to Williams by
the U.S. Tennis Association.



========================================================================== "Line judges need to rule on whether the ball is outside or inside the parameters. Even an error as small as half a degree of visual angle,
equal to a sub-millimeter shift on the judge's retina, may influence
the result of the whole match," said Wang, a die-hard tennis fan.

Researchers sought to understand if different people see objects in
their surroundings exactly the same way. For example, when glancing
at a coffee cup on a table, can two people agree on its exact position
and whether its handle is big enough to grip? The result of a series of experiments suggest not, though there's an upside.

"We may reach for a coffee mug thousands of times in our life, and
through practice we reach our target," Wang said. "That's the behavioral
aspect of how we train ourselves to coordinate how we act in relation
to what we see." In the first task to test visual localization, study participants pinpointed on a computer screen the location of a circular
target. In another experiment looking at variations of acuity within each person's field of vision, participants viewed two lines set a minimal
distance apart and determined whether one line was located clockwise or counterclockwise to the other line.

And in an experiment measuring perception of size, participants viewed
a series of arcs of varying lengths and were asked to estimate their
lengths.

Surprisingly, people perceived the exact same arcs to be bigger at some locations in the visual field and smaller at other locations.

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

"Though our study might suggest that the source of our visual deficiencies
can originate from our brain, further investigations are needed to
uncover the neural basis," said Wang.

"What's also important," she added, "is how we adapt to them and
compensate for our errors." Other co-lead authors of the study are
David Whitney at UC Berkeley and Yuki Murai at UC Berkeley and Osaka
University in Japan.


========================================================================== Story Source: Materials provided by
University_of_California_-_Berkeley. Original written by Yasmin
Anwar. Note: Content may be edited for style and length.


========================================================================== Journal Reference:
1. Zixuan Wang, Yuki Murai, David Whitney. Idiosyncratic perception:
a link
between acuity, perceived position and apparent size. Proceedings
of the Royal Society B: Biological Sciences, 2020; 287 (1930):
20200825 DOI: 10.1098/rspb.2020.0825 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/07/200714144735.htm

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