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Afroditi Panagopoulos, Michael W Grunau, Cesar Galera; Intruder effects in cued visual search. Journal of Vision 2003;3(9):628. doi: 10.1167/3.9.628.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have shown that cueing exogenously and endogenously the area that contains the relevant stimulus locations in visual search is effective, and is sensitive to the shape of the configuration of the relevant stimuli. Results suggested that valid cues correctly guided subjects' attention to the relevant stimuli (VSS 2002). We used this paradigm to measure certain properties of the search light metaphor. Abrupt onsets capture attention when the visual system is in a focused attention mode. We investigated to what extent the intruder would affect visual search. We also examined the difference between the intruder being inside or outside of the focused area and whether the intruder was compatible or incompatible to the target stimulus. Methods: Two configurations (horizontal vs vertical) of 4 stimuli, one of which was the target, were presented. A variable time before the stimuli, either a valid or invalid endogenous cue was given (a letter “V” or “H”). On some trials, an intruder would appear. On the trials where the compatible or incompatible intruder was present, it would appear with a delay of 0, 250 or 5oo ms relative to the stimuli. Results: Valid cueing produced faster response times than invalid cueing. When the intruder was present, target detection was slower than without intruder. It also took longer to find the target when the intruder was inside the attended area. The intruder was most detrimental when it appeared 500 ms after the stimuli. Contrary to expectations, the compatible and incompatible intruder conditions did not differ significantly.
Conclusion: Visual search is influenced by two distinct mechanisms: an automatic and a voluntary mechanism.
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