Subset-Selectivity and Distractor Matching in Visual Conjunction Search
INSTITUTE FOR PERCEPTION RVO-TNO SOESTERBERG (NETHERLANDS)
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In search for a conjunction of color and orientation, Theeuwes, Kaptein and Van der Heijden 1993 obtained target absent responses that were in some conditions faster and in other conditions slower than target present responses. In addition, target absent search function slopes were shallower than target present slopes. These findings cannot be explained by present conjunction search theories. Since in the same study Theeuwes et al. demonstrated subset- selectivity in conjunction search, the interdependence of the fast absent responses and subset-selective search needed to be assessed. The present study shows that subset-selective search is independent of the occurrence of fast absent responses. Experiment 1 replicated the findings of Theeuwes et al. 1993 . Experiment 2 showed that the fast absents were not the result of a response bias. The results of Experiments 3 and 4 showed that the fast absents can be explained by a weak, parallel distractor matching process that enables responding target absent if all relevant distractor elements are similar. Since this process is easily disturbed, the absence of a sameness-signal can not be used for target present decisions. It is argued that both subset-selective search and distractor matching may have unnotedly occurred in previously reported experiments.
- Anatomy and Physiology