ArticleeLife2022
Experimental evidence that uniformly white sclera enhances the visibility of eye-gaze direction in humans and chimpanzees.
Article in eLife, 2022. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Cited by 16 papers.
What it found
Each row is one number read from the abstract, on the scale the paper reported it, with its interval. Left of the dashed line favours the treatment, right favours the comparator. Under each row is the sentence it came from. New to these charts? A ten-minute tutorial.
The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Neither the registry nor the abstract names a trial number. If this is a trial report, that itself is worth knowing.
Who cites it
16 citing papers in PubMed, 25 citations in OpenAlex.
- Rhesus monkeys use both eye and head gaze to reallocate covert spatial attention facilitating visual perception.Cognitive, affective & behavioral neuroscience · 2026Article
- Designing research interfaces for non-human minds: a biocentric design approach for animal cognition research.Animal cognition · 2026Review
- The right eye for fixations: Eye asymmetries modulate gaze patterns towards speakers.Psychonomic bulletin & review · 2026Article
- Visual preference for previously familiar faces in Chimpanzees (Pan troglodytes).Scientific reports · 2026Article
- Developmental trajectories of head and eye cue integration in gaze perception.Scientific reports · 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
- The Apemen Faces Database (ApeFD).Scientific data · 2025Article
- Photoregulatory functions drive variation in eye coloration across macaque species.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
- White sclera is present in chimpanzees and other mammals.Journal of human evolution · 2023Article
- 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 evolutionary drivers of primate scleral coloration.Scientific reports · 2022Article
- Gaze following: A socio-cognitive skill rooted in deep time.Frontiers in psychology · 2022Review
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
3 authors at 3 institutions in 4 countries.
Funding
No grant is acknowledged in the PubMed record.
Abstract
Hallmark social activities of humans, such as cooperation and cultural learning, involve eye-gaze signaling through joint attentional interaction and ostensive communication. The gaze-signaling and related cooperative-eye hypotheses posit that humans evolved unique external eye morphologies, including uniformly white sclera (the whites of the eye), to enhance the visibility of eye-gaze for conspecifics. However, experimental evidence is still lacking. This study tested the ability of human and chimpanzee participants to discriminate the eye-gaze directions of human and chimpanzee images in computerized tasks. We varied the level of brightness and size in the stimulus images to examine the robustness of the eye-gaze directional signal against simulated shading and distancing. We found that both humans and chimpanzees discriminated eye-gaze directions of humans better than those of chimpanzees, particularly in visually challenging conditions. Also, participants of both species discriminated the eye-gaze directions of chimpanzees better when the contrast polarity of the chimpanzee eye was reversed compared to when it was normal; namely, when the chimpanzee eye has human-like white sclera and a darker iris. Uniform whiteness in the sclera thus facilitates the visibility of eye-gaze direction even across species. Our findings thus support but also critically update the central premises of the gaze-signaling hypothesis.
Indexed as
Identifiers
What OpenQuestion holds
Registered trials
Read under generation 80e0d062 · epoch 390. Bibliography from PubMed, PubMed Central and OpenAlex; grants from NIH RePORTER; trial links from ClinicalTrials.gov; estimates, votes and beliefs from the OpenQuestion graph.