Dimension- and space-based intertrial effects in visual pop-out search: modulation by task demands for focal-attentional processing |
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| Authors: | Joseph Krummenacher Hermann J Müller Michael Zehetleitner Thomas Geyer |
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| Institution: | (1) Department of Psychology, University of Fribourg, Rue de Faucigny 2, 1700 Fribourg, Switzerland;(2) General and Experimental Psychology, Ludwig Maximilian University Munich, Munich, Germany;(3) Birkbeck College, University of London, London, UK |
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| Abstract: | Two experiments compared reaction times (RTs) in visual search for singleton feature targets defined, variably across trials,
in either the color or the orientation dimension. Experiment 1 required observers to simply discern target presence versus
absence (simple-detection task); Experiment 2 required them to respond to a detection-irrelevant form attribute of the target
(compound-search task). Experiment 1 revealed a marked dimensional intertrial effect of 34 ms for an target defined in a changed
versus a repeated dimension, and an intertrial target distance effect, with an 4-ms increase in RTs (per unit of distance)
as the separation of the current relative to the preceding target increased. Conversely, in Experiment 2, the dimension change
effect was markedly reduced (11 ms), while the intertrial target distance effect was markedly increased (11 ms per unit of
distance). The results suggest that dimension change/repetition effects are modulated by the amount of attentional focusing
required by the task, with space-based attention altering the integration of dimension-specific feature contrast signals at
the level of the overall-saliency map.
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