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Abstract:
Many studies have shown that when patients with left
hemispatial neglect are shown a horizontal line and asked to draw a
vertical line through its center, they will place the line too far
to the right, suggesting that they underestimate the left side.
However, recent studies have found a cross-over effect, with errors
in the opposite direction for very short lines. Pseudoneglect has
been observed in normal subjects, who tend to place the vertical
line slightly to the left of center, suggesting they overestimate
the left side. This is thought to result from the right hemispheres
role in attention, which biases attention to the left side of
space. There have been no reports of a cross-over effect in normal
subjects, due to the fact that they are almost perfectly accurate
in bisecting short lines. However, this problem can be overcome by
administering the Landmark task. We presented 61 right-handed
adults with pre-bisected lines that were 1, 2, 8, 16, or 28 cm.
long. They were asked to report whether the line was bisected too
far to the left or right. We found a significant cross-over effect.
The center line was reported as too far left for 1 cm lines, and
too far right for longer lines. This suggests they overestimate the
left side of long lines, and the right side of short lines.
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