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Jared Abrams, Antoine Barbot, Marisa Carrasco; Endogenous attention alters the appearance of spatial frequency. Journal of Vision 2009;9(8):131. doi: 10.1167/9.8.131.
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© ARVO (1962-2015); The Authors (2016-present)
Goal: Exogenous, involuntary attention alters the appearance of many visual features including contrast and spatial frequency. Whereas endogenous, voluntary attention also alters contrast appearance, it is unknown whether it alters other basic visual dimensions. Given that endogenous attention flexibly adjusts spatial resolution, whereas exogenous attention always increases spatial resolution, it is unclear whether these two types of attention will have the same effects on the appearance of spatial frequency.
Methods: A central cue prompted observers to attend to one of two peripheral locations or to both locations (focused vs. distributed attention). RSVP letter streams were shown at each location for 1.2 s, followed by two independently tilted Gabors. In focused-attention trials, observers directed attention to the cued stream, while in distributed-attention trials observers monitored both streams for the target letter. A target (letter X) was presented on 20% of trials, and observers indicated target detection by pressing a key. Observers were instructed to report the orientation (left vs. right) of the higher spatial frequency Gabor when they did not detect the target letter. One Gabor was the Standard, whose spatial frequency was fixed, while the other was the Test, whose spatial frequency was randomly chosen from nine levels around the Standard.
Results and Conclusion: RSVP detection performance was better for focused than distributed trials, indicating that attention was effectively deployed. Attentional deployment caused a systematic shift in the psychometric functions for appearance: stimuli at the cued location were perceived as having higher spatial frequency than stimuli at the uncued location. Concurrently, attention improved orientation discrimination performance. A control experiment ruled out a cue-bias explanation of the effect. These results indicate that endogenous attention increases apparent or perceived spatial frequency.
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