Fig 3. Histograms of the boundaries plotted in Fig 2.

The same data was plotted as histograms whose independent variable was the angle (hue). Each of the horizontal panels corresponds to one of the lightness levels tested and the x-axis corresponds to the angular distance in radians measured counterclockwise from the horizontal. Coloured bars represent Condition 1 (chromatic background) results and black bars underneath represent Condition 2 (achromatic background) results. The curves show the rolling average applied to the histogram data (coloured for Condition 1 and black for Condition 2) which has the effect of smoothing out local variability.