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    "headline": "New Theory Explains Why Human Vision Uses Four Primary Colors",
    "dek": "Researchers propose that the natural world's color distribution explains why humans perceive four unique hues.",
    "prose": "Belsten and Berkeley neuroscientist Bruno Olshausen demonstrated that the natural world displays a restricted palette of colors that the human brain represents as combinations of only four pure colors. [^1]\n\nBiologists and linguists have long puzzled over the universal human tendency to see and name colors as a combination of four pure hues: red, yellow, green, and blue. [^2]\n\nResearchers present a direct optimization method for three-dimensional freeform reflectors that transform the light of a finite-étendue source into a prescribed far-field angular intensity distribution. [^3]\n\nMost people and most cultures do not perceive red as a combination of orange or purple, whereas they naturally perceive orange as a combination of yellow and red. [^4]\n\nThe authors parameterize the emission directions in gnomonic coordinates to ensure that every emitted ray intersects the reflector. [^5]\n\nThe method converges reliably within seconds on a single GPU for all examples tested. [^6]\n\nThe reflector profile is represented by a small neural network, specifically a multilayer perceptron, which is trained end-to-end through a differentiable ray-tracing objective. [^7]",
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