Junchao Hu¹, Stephanie Badde², Petra Vetter¹; ¹University of Fribourg, Switzerland, ²Tufts University

In breaking continuous flash suppression (bCFS), a flickering high-contrast mask displayed to one eye suppresses conscious awareness of a visual stimulus shown to the other eye, and one measures the time it takes participants to report the suppressed stimulus becoming visible. Fearful faces have been shown to break through continuous flash suppression faster than neutral faces, which is often interpreted as prioritized processing of fear during unawareness. However, it is unclear whether faster reactions to suppressed fearful faces genuinely reflect prioritized unaware processing, or whether speed differences in reports of breakthrough arise from post-perceptual processes, such as variations in participants' manual response speeds after stimuli reach awareness. Here, we combined bCFS with eye-tracking. By continuously tracking observers' eye movements as they detected suppressed, invisible fearful and neutral faces, we examined the temporal dynamics of eye responses to these faces during suppression and breakthrough. Participants pressed a button to indicate the location of the suppressed face image as soon as they saw parts of it. Additionally, they reported the face’s emotional expression and its visibility after they gave the localization response. Behavioral results showed that participants localized initially suppressed fearful faces faster than neutral faces. Eye-tracking revealed that even before reported awareness of faces, the eyes moved earlier towards suppressed fearful faces than neutral ones. When the faces were superimposed on the flashing mask, thus always visible, manual reaction times and oculomotor responses to fully visible fearful and neutral faces were indistinguishable. Our findings suggest that faster breakthrough RTs of fearful faces are driven by faster eye responses to fearful faces during unaware processing. Our approach avoids potential confounds of post-perceptual and decisional factors associated with RT measures in bCFS. We propose that fearful faces’ ability to attract the eyes, even in the absence of awareness, may facilitate their perceptual detection.

Acknowledgements: This work was supported by a PRIMA grant (PR00P1_185918/1) from the Swiss National Science Foundation to Petra Vetter.