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Joaquim Carlos Rossini, Michael von Grünau; Covert and overt selection on visual search. Journal of Vision 2010;10(7):1321. doi: 10.1167/10.7.1321.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Two experiments were conducted to investigate the effect of covert selection (attentional selection) and overt selection (oculomotor selection) in visual search tasks when the relevant stimuli (target and distractors) were presented among irrelevant stimuli (background). Methods: In the first experiment participants were required to make a visual search for a target accompanied by a variable number of distractors (5, 10, 15) presented among a uniform background with different luminance. The target was a “+” sign with the vertical segment displaced to the right or left of the center of the horizontal segment. In half of the trials an element with the same characteristics as the target, but with the same luminance as the background and with the vertical segment displacement in the opposite direction, was presented (intruder element). Targets, distractors and the intruder element were presented in random positions within the matrix. In the second experiment the same procedure was adopted, but the relevant stimuli (target and distractor) and irrelevant stimuli (intruder and background) differed along a colour dimension with equiluminance. Reaction time and percentage of eye fixations were measured. Results: The presence of the intruder played a role during attentional selection (covert selection) and caused a reaction time cost but did not show a significant effect in oculomotor selection (overt selection), evidenced by a non-significant percentage of fixations on intruder element. Conclusions: The results support the independent selection model and are discussed in terms of stimulus-driven activity and goal-driven control on visual search.
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