(A) Continuous flash suppression was used to suppress low-contrast emotional face stimuli from awareness: when a high-contrast colored flickering mask is presented to the dominant eye (using a stereoscope) the viewer will not be aware of the picture presented to the non-dominant eye for several seconds. (B) Face stimuli with either a neutral, angry, or fearful expression (10 identities, five male, five female; see Materials and methods) were presented to the non-dominant eye. Faces were placed in any of the 4 quadrants of the stimulus field, either upright or upside down (to control for low-level visual features). (C) After a mandatory fixation period of 200 ms, the face stimulus was gradually faded in for 500 ms and fully presented to the non-dominant eye for 1000 ms while the flickering mask was continuously presented to the dominant eye. The mask was displayed for a further 200 ms to prevent aftereffects of the face stimulus. At the end of each trial, participants indicated the location of the face stimulus, its emotional expression, and its visibility by a button press.
© 1998 Karolinska Institutet. All rights reserved. Face stimuli in panels A, CB, and C are reproduced, with permission, from The Karolinska directed emotional faces (KDEF) (Lundqvist et al., 1998). These images are not available under CC-BY and are exempt from the CC-BY 4.0 license. They may not be redistributed or shared without written consent from the copyright holder (Karolinska Institutet, Psychology section). The ID for the face depicted in this figure is AM10 and the IDs for the faces used in experiments are AM05, AM06, AM08, AM10, AM17, AF01, AF09, AF14, AF19, and AF20.