Abstract
Three pigeons worked on visual search tasks in which arrays of 32 small forms appeared in computer-driven displays. Their task was to peck at a unique target among identical distractors; the main dependent variable was the speed with which this target was found. The target and distractor forms for each trial were chosen from a set of forms (usually 16); in most experiments, all possible pairs of forms appeared in each experimental session. Six experiments were run; each yielded a matrix of mean reaction times (RTs), one for each of the form pairs. Such matrices were subject to multidimensional scaling, from which best-fitting interform distances were determined. In four experiments with disparate form sets, Euclidean distance between pairs of forms in multidimensional space was found to approximate an exponential decay function of RT-K, whereK was a constant set for each subject. Two additional experiments showed that RT distributions for single-form pairs were well fit by the convolution of a fixed distribution, approximately Gaussian, and an exponential distribution whose decay parameter varied with interform similarity. The exponential decay parameter may be taken to reflect momentary detection probability, and interform distance in multidimensional space may be taken to measure similarity. Thus, the data as a whole suggest an exponential relation between the probability of detecting a target and the similarity of that target to its surrounding distractors. This relationship is analogous to Shepard’s law of generalization, which states an exponential relation between response probability and similarity.
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This research was supported in part by National Science Foundation Grant BNS-8025515.
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Blough, D.S. Quantitative relations between visual search speed and target-distractor similarity. Perception & Psychophysics 43, 57–71 (1988). https://doi.org/10.3758/BF03208974
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DOI: https://doi.org/10.3758/BF03208974