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Carrasco, M., McLean, T.L.,
Katz, S.M. & Frieder, K.S. (1998). Feature asymmetries in visual search:
Effects of display duration, target eccentricity, orientation & spatial
frequency. Vision Research, 38(3): 347-374.
Abstract
In Experiments 1-3, we monitored search performance as a function of target
eccentricity under display durations that either allowed or precluded
eye movements. The display was present either until observers responded,
for 104 msec, or for 62 msec. In all three experiments an rientation asymmetry
emerged: observers detceted a tilted target among vertical distracters
more efficiently than a vertical target among vrtical distracters. As
target eccentricity increased, reaction times and errors augmented, and
the size effect beacme more pronounced, more so for vertical than tilted
targets. In Experiments 4-7, the stimulus spatial properties were manipulated:
spatial frequency; size; and orientation. The eccentricity effect was
more pronounced for vertical than tilted targets for high- than low-spatial
frequency targets. This effect was eliminated when either the size, the
size and orientation, or the size ans spatial frequency were magnified
(M-cortical factor). By increasing the signal-to-noise ratio, magnification
reduced the extent of both asymmetries; it aided more the detection of
tilted than vertical and of high- than low-spatial fequency targets. Experiments
4-7 indicate that performance improvement in the magnified conditions
was due to the specific pairing of stimulus size with the retinal eccentricity
and not to the larger stimulus size of the magnified conditions. We conclude
that stimulus size, orientation and spatial frequency influence the extent
of the eccentricity effect and the efficiency of search peformance.
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