Researchers were able to determine that study participants were looking at this street scene even when the participants were only looking at the outline. Courtesy of Fei-Fei Li |
Researchers
call it mind reading. One at a time, they show a volunteer – who’s
resting in an MRI scanner – a series of photos of beaches, city streets,
forests, highways, mountains and offices. The subject looks at the
photos, but says nothing.
The
researchers, however, can usually tell which photo the volunteer is
watching at any given moment, aided by sophisticated software that
interprets the signals coming from the scan. They glean clues not only
by noting what part of the brain is especially active, but also by
analyzing the patterns created by the firing neurons. They call it
decoding.
Now,
psychologists and computer scientists at Stanford, Ohio State
University and the University of Illinois at Urbana–Champaign have taken
mind reading a step further, with potential impact on how both
computers and the visually impaired make sense of the world they see.
The
researchers, including Stanford computer scientist Fei-Fei Li, removed
almost all of the detail from the color photographs, leaving only sparse
line drawings of the assorted scenes. When they ran the experiment
again with just the outlines, the researchers were still able to read
the minds of the participants – with as much accuracy as before.
The
research was focused on the parahippocampal place area, a region of the
brain that plays an important role in recognition of scenes such as
rooms, landscapes and city streets.
The
results demonstrate that outlines play a crucial role in how the human
eye and mind interpret what is seen. The bare outlines of the photos
shown to the participants seemingly offered the brain almost as many
clues as the original photo. This “impoverished” signal sent to the
brain was enough, Li said.
The drawing of a dog as part of the Nazca Lines geoglyphs, Peru, ca. 700–200 B.C. suggests the power of outlines throughout time. Steve Taylor / Creative Commons |
The
significance of the work? “By noting what is driving the brain, you
will be learning the way the brain works,” Li said, “why certain cues
are more important than other cues.”
“Mind
reading” could prove helpful in assessing patients in comas. “Inferring
what people are seeing is clinically important,” Li said.
The
power of outlines seems backed up by history and common experience. As
the authors wrote in their research paper, published in the Proceedings
of the National Academy of Sciences, early cave dwellers drew outline
figures on the walls of their homes; Chinese calligraphy revolves around
lines and strokes; and children draw outlines as they attempt to
describe the world unfolding before them.
“The
representations in our brain for categorizing these scenes seem to be a
bit more abstract than some may have thought – we don’t need features
such as texture and color to tell a beach from a street scene,” said
Dirk Bernhardt-Walther, a psychologist at Ohio State University who was a
member of the research team.
Even
when the software made errors reading the black-and-white line drawing
of, for example, the beach, the mistakes closely resembled the mistakes
made with the color photo of the beach, underscoring the conclusion that
line drawings stimulate the mind in almost the same way as color
photographs.
As
researchers began removing parts of the line drawings piece by piece
before showing them to the participants, they learned that the longer
contours created by the lines, which formed the structure of the scene,
were the most important.
“Lines capture really important structure, and you can find evidence of that in the brain,” Li said.
