Figure 2.

Opponency compared with relative brightness in M. salmoides visual detection model for training colors (chartreuse yellow, white, red, blue, green, and black) and achromatic stimuli used in assay 3 (white, gray 1, gray 2, gray 3, gray 4, gray 5, and black). If bass use only achromatic cues, then bass should be unable to distinguish red from gray 1 or gray 2, blue and green from gray 4/black, and yellow from white, as these stimuli have similar brightness.