Figure 4.

Change in pupil diameter for all observers (a) under the mRGC condition, (b) under the luminance condition and (c) under the energy condition. The horizontal axis represents relative excitation and the vertical axis represents change in pupil diameter for all observers. The dashed line shows the regression line averaged across all observers. The values of the slopes of the regression line are provided in the upper right in the panel and the 95% confidence limits for the slope are given in brackets. Circle, DO; triangle, HE; square, KH; diamond, NY; inverted triangle, SS; cross, YT. (d) The relative contribution of mRGC and L + M luminance signals to all photoreceptor classes at each relative receptor excitation (filled black bar, mRGC; filled grey bar, luminance). The change in pupil diameter under the mRGC and luminance conditions (figure 4a,b) normalized with respect to the change under the energy condition (figure 4c).