Contrast Negation and the Importance of the Eye Region for Holistic Representations of Facial Identity Mladen Sormaz, Timothy J. Andrews, and Andrew W. Young University of York Reversing the luminance values of a face (contrast negation) is known to disrupt recognition. However, the effects of contrast negation are attenuated in chimeric images, in which the eye region is returned to positive contrast (S. Gilad, M. Meng, & P. Sinha, 2009, Role of ordinal contrast relationships in face encoding, Proceedings of the National Academy of Sciences, USA, Vol. 106, pp. 5353–5358). Here, we probe further the importance of the eye region for the representation of facial identity. In the first experiment, we asked to what extent the chimeric benefit is specific to the eye region. Our results showed a benefit for including a positive eye region in a contrast negated face, whereas chimeric faces in which only the forehead, nose, or mouth regions were returned to positive contrast did not significantly improve recognition. In Experiment 2, we confirmed that the presence of positive contrast eyes alone does not account for the improved recognition of chimeric face images. Rather, it is the integration of information from the positive contrast eye region and the surrounding negative contrast face that is essential for the chimeric benefit. In Experiment 3, we demonstrated that the chimeric benefit is dependent on a holistic representation of the face. Finally, in Experiment 4, we showed that the positive contrast eye region needs to match the identity of the contrast negated part of the image for the chimera benefit to occur. Together, these results show the importance of the eye region for holistic representations of facial identity. Keywords: face recognition, eyes, photo negation, contrast chimera, contrast Reversing the luminance values of an image (contrast negation) disrupts the recognition of familiar faces (Galper, 1970; Galper & Hochberg, 1971; Phillips, 1972; Johnston, Hill, & Carmen, 1992). The effect of contrast negation provides an interesting counterex- ample to the typical resistance of familiar face recognition to other types of image degradation (Bruce & Young, 2012), and contrast negation appears to disrupt face recognition to a greater degree than recognition of other types of visual stimuli (Vuong, Peissig, Harrison, & Tarr, 2005; Nederhouser, Yue, Mangini, & Bieder- man, 2007). The effect of contrast negation is easily seen (by those old enough to remember chemical photography) in the difficulty of recognizing faces from photographic negatives. However, the neg- ative of a normal color image reverses both its luminance and its hue. A seminal study by Kemp, Pike, White, and Musselman (1996) demonstrated that face images with negated luminance but normal hue saw a reduction in recognition accuracy, whereas faces with negated hue and normal luminance showed no recognition accuracy decrease. It is therefore clear that information critical to face recognition is somehow carried through luminance values. The explanation for why contrast reversal has such a profound effect on face recognition has been dominated by two different ideas. The first is Kemp et al.’s (1996) suggestion that the diffi- culty in recognizing contrast negated faces is due to the reversal of three-dimensional (3D) shape from shading cues. Their underlying premise is that disrupting depth cues through contrast reversal interferes with the use of information about 3D shape. However, more recent studies have tended to downplay the potential role of 3D information in face recognition and place more emphasis on the importance of surface pigmentation (Bruce & Young, 2012). For example Liu, Collin, and Chaudhuri (2000) found that recog- nition was poor for faces with intact 3D information but missing surface pigmentation. In line with such findings, Bruce and Lang- ton (1994) developed the second main approach to the impact of contrast negation by suggesting that it exerts its disruptive influ- ence because it reverses the brightness of important pigmented regions of the face, so that light regions of skin become dark, dark hair becomes light, and so forth. Recent work expanding on this hypothesis has been carried out by Russell, Sinha, Biederman, and Nederhouser (2006), who propose that much of the contrast nega- tion effect results from negating pigmentation cues that carry substantial information about facial identity. This has been elabo- rated by Sinha, Russell, and their colleagues (Sinha, Balas, Os- trovsky, & Russell, 2006; Russell & Sinha, 2007) into a more general claim that because pigmentation carries much information about facial identity, any manipulation (e.g., contrast negation) that disrupts pigmentation rather than shape will have deleterious effects on recognition. Consistent with this hypothesis, further work by Santos and Young (2008) shows that contrast negation effects are not only confined to identity judgments but also impact on a range of social inferences made to faces in which pigmenta- tion cues are likely to play a substantial role. Importantly, too, a study by White (2001) showed a degree of independence of This article was published Online First May 13, 2013. Mladen Sormaz, Timothy J. Andrews, and Andrew W. Young, Depart- ment of Psychology, University of York, UK. We thank Mel Irwin and Emily Lloyd, whose undergraduate project provided pilot assessments for some of the experiments reported here, though in the event none of their data were used. Correspondence concerning this article should be addressed to Mladen Sormaz, Department of Psychology, University of York, Heslington, York YO10 5DD, UK. E-mail: ms930@york.ac.uk This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Journal of Experimental Psychology: Human Perception and Performance © 2013 American Psychological Association 2013, Vol. 39, No. 6, 1667–1677 0096-1523/13/$12.00 DOI: 10.1037/a0032449 1667