The face stimuli consisted of grayscale photographs of four male identities, each displaying a neutral, angry and fearful expression. Images were taken from the NimStim Face Stimulus Set (Tottenham et al.,
2009) and the Karolinska Directed Emotional Faces (KDEF) image set (Lundqvist & Litton,
1998). We confined our stimuli to male faces only as male and female faces have been shown to differentially influence recognition of angry expressions (Becker, Kenrick, Neuberg, Blackwell, & Smith,
2007). The hair and non-facial areas were removed from the photographs so that only the central face area was visible (
Figure 1). Face images subtended a visual angle of approximately 12° × 8°. Gaze direction was manipulated using Adobe Photoshop (
http://www.adobe.com/); as used in other studies (Adams, Gordon, Baird, Ambady, & Kleck,
2003; Adams & Kleck,
2005; Graham & LaBar,
2007). The position of the iris of both eyes was shifted to the left or the right at incremental steps of one pixel per image, equivalent to a shift of 0.03 cm, or a visual angle of approximately 5′ minutes of arc viewed from a distance of 50 cm. The images were selected from a set of angry, fearful and neutral faces that had been rated for valence and arousal by a group of 16 participants, who did not take part in the current study. Ratings showed that fearful and angry faces did not differ on measures of arousal (Z = 0.59,
p = 0.99) or valence (Z = 1.74,
p = 0.18; sidak corrected). Thus, any differences in gaze discrimination cannot be attributed to differences in arousal and valence alone.