A TETRACHROMATIC HYPOTHESIS FOR HUMAN COLOR VISION

The hypothesis is advanced that human foveal color vision might be tetrachromatic at the first, or photopigment, stage, with immediate convergence to three channels. Evidence taken to support this is: the breakdown of color matches at high intensities ; the similarity of the breakdown condition to protanomaly ; the questionableness of the high-density hypothesis ; the failure of the submaximum of the luminosity curve at 605 nm to shift with selective adaptation : and the marked reduction of this submaximum at high intensities. © 1969.