ArticleScientific reports2021
Ocular pigmentation in humans, great apes, and gibbons is not suggestive of communicative functions.
Article in Scientific reports, 2021. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 18 papers.
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18 citing papers in PubMed, 38 citations in OpenAlex.
- Rhesus monkeys use both eye and head gaze to reallocate covert spatial attention facilitating visual perception.Cognitive, affective & behavioral neuroscience · 2026Article
- Gaze in context: non-human eyes can be more salient under ecologically relevant conditions.Evolutionary human sciences · 2026Article
- Scleral exposure influences social judgments of trustworthiness, attractiveness, sociability, and social rank in White faces.PloS one · 2026Article
- Look past the cooperative eye hypothesis: reconsidering the evolution of human eye appearance.Biological reviews of the Cambridge Philosophical Society · 2025Review
- Photoregulatory functions drive variation in eye coloration across macaque species.Scientific reports · 2024Article
- Preliminary evidence that eye appearance in parrots (Psittaciformes) co-varies with latitude and altitude.Scientific reports · 2024Article
- Are dark-eyed dogs favoured by humans? Domestication as a potential driver of iris colour difference between dogs and wolves.Royal Society open science · 2023Article
- Human-specific genetics: new tools to explore the molecular and cellular basis of human evolution.Nature reviews. Genetics · 2023Review
- Depth from motion parallax: Deictic consistency, eye contact, and a serious problem with Zoom.Journal of vision · 2023Article
- Scleral appearance is not a correlate of domestication in mammals.Zoological letters · 2023Article
- White sclera is present in chimpanzees and other mammals.Journal of human evolution · 2023Article
- Is there no beauty in sexually dimorphic eyes? Facial attractiveness and White Europeans ocular morphology-Brief communication.PloS one · 2023Article
- Attention Towards Pupil Size in Humans and Bonobos (Affective science · 2022Article
- The adaptive significance of human scleral brightness: an experimental study.Scientific reports · 2022Article
- Ecological factors are likely drivers of eye shape and colour pattern variations across anthropoid primates.Scientific reports · 2022Article
- The gaze of a social monkey is perceptible to conspecifics and predators but not prey.Proceedings. Biological sciences · 2022Article
- Chimpanzee (Pan troglodytes) gaze is conspicuous at ecologically-relevant distances.Scientific reports · 2022Article
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Authors and funding
4 authors at 2 institutions in 2 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Pigmentation patterns of the visible part of the eyeball, encompassing the iris and portions of the sclera, have been discussed to be linked to social cognition in primates. The cooperative eye hypothesis suggests the white sclera of humans to be a derived adaptive trait that enhances eye-mediated communication. Here, we provide a comparative analysis of ocular pigmentation patterns in 15 species of hominoids (humans, great apes & gibbons) that show marked differences in social cognition and quantify scleral exposure at the genus level. Our data reveals a continuum of eye pigmentation traits in hominoids which does not align with the complexity of gaze-mediated communication in the studied taxa. Gibbons display darker eyes than great apes and expose less sclera. Iridoscleral contrasts in orangutans and gorillas approach the human condition but differ between congeneric species. Contrary to recent discussions, we found chimpanzee eyes to exhibit a cryptic coloration scheme that resembles gibbons more than other apes. We reevaluate the evidence for links between social cognition and eye pigmentation in primates, concluding that the cooperative eye hypothesis cannot explain the patterns observed. Differences in scleral pigmentation between great apes and humans are gradual and might have arisen via genetic drift and sexual selection.
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