Abstract
In a visual feature search task, reaction times to a singleton target are known to be shorter when participants have advance knowledge of the defining-features of targets. The present study examined whether the prior-knowledge effect is influenced by search modes (feature vs. singleton). In addition, using a variant of the flanker task, the present study assessed whether prior-knowledge affected efficiency of attentional focusing to a target. When participants performed a target discrimination task (i.e., compound search task), using a singleton detection mode, no prior-knowledge effect was found (Experiments 1 and 3). However, when the same task was performed using a feature search mode, prior-knowledge facilitated performance (Experiment 2). This suggests that the dimension weighting of a target-defining feature is modulated by the search mode. Also flanker response congruency was affected by prior-knowledge suggesting that the dimension weighting correlated with attentional focusing to targets. On the other hand, inter-trial dimensional priming was not affected by the search mode. Implications for mechanisms of feature-based top-down control of attention in visual feature search are discussed.
Highlights
Previous studies have reported that prior knowledge of the targetdefining feature dimension facilitate detection of a target in visual search tasks (Treisman, 1988; Müller et al, 1995; Found and Müller, 1996)
Even when the defining-feature dimension of targets was known prior to target presentation, the spatial selection of targets was as inefficient as in conditions when a target dimension was unknown in advance
GENERAL DISCUSSION In this study, the cross-dimensional cost (CDC) was found in a compound search task when participants were forced not to adopt the singleton detection mode, by changing the context of target displays
Summary
Previous studies have reported that prior knowledge of the targetdefining feature dimension facilitate detection of a target in visual search tasks (Treisman, 1988; Müller et al, 1995; Found and Müller, 1996). In one experiment of her study, targets were defined by dimensions of color, orientation, or size in a feature search task. A target feature value of blue was fixed for the color dimension within a block of trials (e.g., a blue bar among green bars). Within the color dimension a target feature might assume different values within a trial block (e.g., either blue, red, or white bar among green bars). The third prior knowledge condition, the cross-dimension condition, defined targets as any one of three feature dimensions (color, orientation, or size). Because defining dimensions of targets were unspecified in the cross-dimension condition but not in the within-dimension condition, the latter allows for advantageous use of dimensional knowledge in target detection
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