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Abstract:
Abstract: Discriminating the direction of movement of a
point-light walker (PLW; Johansson, 1973) requires global
integration of the local motion signals associated with individual
lights attached to the joints of an invisible human form. These
displays should pose problems for individuals with Williams
Syndrome (WS) who have a genetic disorder disrupting various
aspects of spatial cognition, including perception of global motion
(Atkinson et al., 1997) and global organization of local elements
(Bellugi et al., 1988). We found that WS children were comparable
to both mental age-matched and adult control groups in their
ability to discriminate a variety actions portrayed in point-light
displays e.g. walking, cartwheels and falling. In addition, all
three groups were comparable in their ability to perceive the
(right/left) direction of the walking motion of a PLW that was
embedded in dynamic noise which mimicked the local motion of lights
on the PLW. The unpredicable location of the PLW in the display,
and the removal of local motion cues, ensured that directional
discrimination of the PLW could only be achieved by the interaction
of object and motion information. The results of this study
demonstrate that WS individuals are unimpaired in perceiving
biological motion. Therefore, severe impairment in spatial
representation may co-exist with intact perception of biological
motion.
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