General chromatic and achromatic constrasts for dichromats and trichromats.

Mean chromatic (A) and achromatic (B) contrast, between genitalia and thighs of pregnant females, modeled for dichromatic and trichromatic vision. All JND scores (from four females, six weeks and three different phenotypes) presented in Fig 2 have been averaged for each phenotype. The black horizontal line indicates the perceptual threshold of 1 JND (A). Whiskers represent the standard error of the mean.