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dc.contributor.authorMayhew, Jessica
dc.contributor.authorGomez, Juan-Carlos
dc.identifier.citationMayhew , J & Gomez , J-C 2015 , ' Gorillas with white sclera : a naturally occurring variation in a morphological trait linked to social cognitive functions ' , American Journal of Primatology , vol. 77 , no. 8 , pp. 869-877 .
dc.identifier.otherPURE: 175351100
dc.identifier.otherPURE UUID: 3e6be2b3-9db4-4b41-becd-c40b05f5477a
dc.identifier.otherScopus: 84937977431
dc.identifier.otherWOS: 000358678900005
dc.identifier.otherORCID: /0000-0002-0218-9834/work/64361106
dc.descriptionFunding: Self-funded PhD.en
dc.description.abstractHuman eye morphology is considered unique among the primates in that humans possess larger width/height ratios (WHR), expose a greater amount of visible sclera (SSI; width of exposed eyeball/width of visible iris), and critically, have a white sclera due to a lack of pigmentation. White sclera in humans amplifies gaze direction, whereas the all-dark eyes of apes are hypothesized to conceal gaze from others. This study examines WHR and SSI in humans (N = 13) and gorillas (N = 85) engaged in direct and averted gazes and introduces a qualitative assessment of sclera color to evaluate variations in sclera pigmentation. The results confirm previous findings that humans possess a larger WHR than gorillas but indicate that humans and gorillas display similar amounts of visible sclera. Additionally, 72% (N = 124) of gorilla eyes in this sample deviated from the assumed all-dark eye condition. This questions whether gaze-camouflage is the primary function of darkened sclera in non-human primates or whether other functional roles can be ascribed to the sclera, light or dark. We argue that white sclera evolved to amplify direct gazes in humans, which would have played a significant role in the development of ostensive communication, which is communication that both shows something and shows the intention to show something. We conclude that the horizontal elongation of the human eye, rather than sclera color, more reliably distinguishes human from great ape eyes, represented here by gorillas.
dc.relation.ispartofAmerican Journal of Primatologyen
dc.rights© 2015 Wiley Periodicals, Inc. This is the accepted version of the following article: Mayhew, J., & Gomez, J-C. (2015). Gorillas with white sclera: a naturally occurring variation in a morphological trait linked to social cognitive functions. American Journal of Primatology 77:869-877, which has been published in final form at
dc.subjectWhite scleraen
dc.subjectGaze camouflagingen
dc.subjectEye morphologyen
dc.subjectGaze followingen
dc.subjectRC0321 Neuroscience. Biological psychiatry. Neuropsychiatryen
dc.subjectBF Psychologyen
dc.titleGorillas with white sclera : a naturally occurring variation in a morphological trait linked to social cognitive functionsen
dc.typeJournal articleen
dc.contributor.institutionUniversity of St Andrews.School of Psychology and Neuroscienceen
dc.contributor.institutionUniversity of St Andrews.Institute of Behavioural and Neural Sciencesen
dc.contributor.institutionUniversity of St Andrews.Centre for Social Learning & Cognitive Evolutionen
dc.description.statusPeer revieweden

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