Figure 2. The psychometric function relating the choice of “more blue dots” to the log of the ratio of number of blue to yellow dots (gray and black dots are used here to represent yellow and blue, respectively). Data points are the average across dyads (black, N = 15), the more sensitive members of dyads (dark gray curve and circles, N = 15) and less sensitive member members of dyads (light gray curve and circles, N = 15). The curves are best the fitting cumulative normal.