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Emma Ferneyhough, Damian Stanley, Elizabeth Phelps, Marisa Carrasco; Effects of faces as exogenous cues are dependent on visual field and handedness. Journal of Vision 2009;9(8):125. doi: 10.1167/9.8.125.
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Background and Goal. Faces are unlike other visual objects we encounter on a daily basis. They openly display the mental states of others and are thus effective cues to potentially relevant information. The right hemisphere of the human brain has a dominant role in both face processing and spatial attention, a lateralization that has proven to be stronger in right- than left-handers. Here we demonstrate behavioral evidence for an effect of handedness in tasks requiring face processing and attention.
Method. We used non-predictive, peripheral cues to direct exogenous (involuntary) attention to a visual task stimulus. Cues were either faces (Experiment 1) or dots (Experiment 2), and were presented to the upper-left, -right, or both upper quadrants of the visual field. Observers performed an orientation discrimination task with contrast-varying stimuli (3-56% contrast, 4-cpd Gabor patches presented at 5° eccentricity) appearing 125ms after cue onset in either the lower-left or -right visual field. Attention was thus cued to the location of a tilted target (valid cue), a vertical distracter (invalid cue), or distributed over both locations.
Results and Conclusion. We found that for face-cues, contrast sensitivity (CS) modulation depended on the attention condition in right- but not left-handers. Right-hander CS was greatest on valid trials, and lowest on invalid trials, but there was no left-hander CS difference. Furthermore, an interaction between target visual field and handedness was observed for both CS and reaction time. For dot cues, however, CS depended on attention across both visual fields and handedness conditions. These results demonstrate that the use of social stimuli such as faces alters the effects of attention, likely due to the visual system's asymmetric treatment of such stimuli. The handedness-dependent face-processing asymmetry may explain the presence of attention effects in right-handers and its absence in left-handers.
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