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DanpikeronMastodon9d ago
This illusion was new to me. Does whichever dot you look at turn more purple?
Pretty neat how clearly this lets you see the reduced sensitivity to blue light in the very centre of your vision.
https://www.schulz-hildebrandt.com/9-purple-dots-illusion/
https://arxiv.org/abs/2509.11582
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Analysis Summary
A user shared a visual illusion that demonstrates a well-known quirk of human vision — the fovea (center of the retina) has very few blue-sensitive cones, so you perceive blue less strongly at the exact point you're focused on. The explanation matches established vision science, and the post links to both the illusion and an arxiv paper for those curious. Worth noting: this is the same biological reason astronomers often use averted vision to see faint blue stars more clearly.
Claims Analysis (2)
“This optical illusion demonstrates reduced sensitivity to blue light in the very centre of vision”
The fovea has lower density of S-cones (blue-sensitive), causing reduced blue sensitivity at the visual center — well-established in vision science.
“The linked illusion is hosted at schulz-hildebrandt.com and described in arxiv paper 2509.11582”
Cannot directly verify the arxiv paper or hosted illusion, but the references appear to be specific and consistent with academic vision research.
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