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Abstract:
For the past 20 years, a number of studies has suggested that
the right hemisphere (RH) may have a limited involvement in higher
cognitive processes (e.g., Gazzaniga & Smylie, 1984). Lesion
studies, however, indicate that the RH plays an important role in
several visuoperceptual abilities. The purpose of the present study
was to determine the relative ability of each hemisphere to carry
out a visuospatial skill learning which should primarily engage the
RH. Sixty right-handed subjects (mean age: 23) were shown a
lateralized version of the fragmented picture task (Snodgrass,
Smith, Feenan, & Corwin, 1987). Subjects were divided into four
groups (n=15) following two criteria: 1) modality of response
(manual or verbal), 2) trained hemisphere (left or right). The task
consisted in pressing a button (manual condition) or naming the
stimulus (verbal condition) as soon as the fragmented object was
recognized. In the manual response condition, the RH showed a
decrease in perceptual thresholds during training but the left
hemisphere (LH) showed no implicit learning. The LH, however, was
able to learn just as well as the RH when a verbal identification
was required. These data indicate that a verbal mode of response or
semantic encoding may overshadow the unique competences of the RH
in certain cognitive tasks.
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