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Michael von Grünau, Cesar Galera, Afroditi Panagopoulos, Mikael Cavallet; Exogenous attention distorts visual space and speeds up processing: Effects on apparent size. Journal of Vision 2006;6(6):220. doi: https://doi.org/10.1167/6.6.220.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Exogenous selective attention can be employed to a restricted region in space by using a brief peripheral cue. Subsequently presented stimuli in this region are processed in ways that give them a competitive advantage (e.g. discriminability and contrast sensitivity are increased, response time is decreased, apparent contrast is increased). We used two kinds of cues to assess how apparent size is altered by attention. Methods: Peripheral cues were a briefly flashed small spot or an outline circle, always with central fixation. Test lines or squares were flashed at the cue location and at a symmetrical position. Size equivalence was determined by a 2AFC method. Temporal order (TO) and response time (RT) were also determined in the same situations. Results: Apparent size at the cued location was judged to be larger with the spot cue, but smaller with the circle cue, as compared to the uncued position. When both cues were used, the two opposite effects on apparent size were canceled when the two cues were simultaneous, but otherwise were in accordance with the effect of the last cue displayed. TO and RT measures indicated that the cued stimulus was processed faster and appeared ahead temporally for both cue types. In all cases, the effects were largest for short cue-test intervals. Conclusion: Exogenous cues distort space for brief periods in such a way that stimulus edges are repelled from the cue center. Temporal effects, however, are uniform and independent of cue type.
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