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Carrasco, M., Evert, D.L., Chang,
I. & Katz, S.M. (1995). The eccentricity effect: Target eccentricity affects
performance on conjunction searches. Perception & Psychophysics,
57(8): 1241-1261.
Abstract
The serial pattern found for conjunction visual search tasks has been
attributed to covert attentional shifts, even though the possible contributions
of target locations have not been considered. To investigate the effect
of target location on orientation * color conjunction searches, the target's
duration and its position in the display were manipulated. The display
was present either until observers responded (Experiment 1), for 104 ms
(Experiment 2) or for 62 ms (Experiment 3). Target eccentricity critically
affected performance: A pronounced eccentricity effect was very similar
for all three experiements; as eccentricity increased, reaction times
and errors increased gradually. Furthermore, the set-size effect became
more pronounced as eccentricity increased, and the extent of eccentricity
effect increased for larger set sizes. In addition, according to stepwise
regressions, target eccetricity as well as its interactions with set size
were good predictors of performance. We suggest that these findings could
be explained by spatial-resolution and lateral-inhibition factors. The
serial self-terminating hypothesis for orientation * color conjunction
searches was evaluated and rejected. We compared the eccentricity effect
as well as the extent of orientation asymmetry in these three conjunction
experiments with those found in feature experiements (Carrasco & Katz,
1992). The roles of eye movements, spatial resolution, and covert attention
in the eccentricity effect, as well as their implications, are discussed.
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