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UD professor examines spatial deficits in Williams
syndrome children
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| Above (middle two rows) are samples of
copied spatial designs (top row) by two 11-year-old
children with Williams Syndrome. Typically, their copies
distort spatial properties while preserving other design
aspects, such as color. The drawings in the bottom row are
by a six-year-old child without Williams syndrome. |
1:15 p.m., May 28, 2004--Approximately
one in 25,000 individuals worldwide are born with Williams
syndrome (WS), a rare, genetically based disorder resulting
in mild mental retardation and an unusual pattern of
strengths and weaknesses in cognitive abilities.
Individuals with WS may have language and social skills but
still can be profoundly impaired in visual-spatial
abilities and numeric processing. For example, a Williams
syndrome child of 11 may be unable to draw a picture of a
ball with two colors but have no difficulty describing it.
James Hoffman, professor of psychology at the University of
Delaware, and Barbara Landau, Dick and Lydia Todd Professor
of Cognitive Science at Johns Hopkins University, are using
eye-tracking measures to detail the nature of the spatial
deficit and how it affects descriptive language with the
goal of understanding more completely how the brain is
organized. Their work is funded by grants from the March of
Dimes, National Science Foundation and National Institutes
of Health.
Hoffman’s research centers on spatial cognition,
particularly visual attention and eye movements. His focus
is on the role of attention in the performance of
"real-world tasks," such as searching for an object in a
cluttered scene or constructing spatial patterns. He uses
standard models from cognitive psychology as well as
measuring “event-related brain potentials” and eye
movements.
Landau studies language learning, spatial representation
and the relationships between these systems of knowledge.
In their laboratory work, Hoffman and Landau have
children with and without WS of various ages do spatial
construction or, in this case, reproduce images on paper.
They then track and record the children’s eye movements as
they try to complete the task. Hoffman said that tracking
the eye movements gives them an understanding of how the
brain is working and of the nature of the deficit.
“These kids are giving us a window on mapping the
brain/mind,” Hoffman said.
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| James Hoffman, profesor of psychology
(left), works with Anthony, 14, to record eye movements
during various tasks. Photo by Jack Buxbuam. |
He and Landau have pinpointed a variety of
deficits and areas of the brain that are responsible for
performing spatial tasks, and they are trying to understand
if the brain malfunctions when observing the object or in
reproducing it and why.
“We believe that the spatial distortions we see in
drawings and other visio-spatial construction tasks by
people with Williams syndrome do not reflect corresponding
distortions in their perception of the world. We will argue
that this syndrome leaves spared a number of spatial
cognitive subsystems, including object recognition and
identification, biological motion perception and spatial
languageŠand that some of the most profound deficits are
not due to abnormal architecture, but to small
misadjustments that culminate in large downward spiraling
performance.”
One example of this, Hoffman said, is that persons with
WS know that their drawings are not correct. The most
common errors involved choosing an incorrect part and
drawing it in an incorrect location. They can easily
distinguish between correct and incorrect drawings of
models, but they can’t do better when they try again, he
said.
“Drawing or assembling parts to make a model is an
extremely frustrating experience for them because they are
aware of their poor abilities in this domain, and they
usually resort to random changes in an effort to correct
their efforts. However, the defect is not simply a problem
with motor output either because they can trace drawings
just fine. So their spatial deficits are not due simply to
either problems in input (perception) or output (action)
but to some cognitive processes in between. We are now
trying to characterize the nature of these processes,” he
said.
Article by Barbara Garrison
Photo and graphics courtesy of the Department of Psychology
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