Original art paintings are chosen over their "color-rotated" versions because of changed color contrast.

Rotating colors (digitally within CIELAB color space) of an artistic painting is thought to keep constant all aspects of the painting except the hues. When observers are asked to select the preferred image among color-rotated images the "original" version of the artwork is typically selected, while the hue transformed images are rejected. We hypothesized that color contrast may be reduced after such digital rotations, which was supported by feature analyses. We also found that when the original painting or rotations were viewed individually, they did not differ in both hedonic ratings and pupil responses, though observers selected the original paintings in a forced-choice test. Hence, we generated versions of the paintings where color contrast was either enhanced or reduced and forced-choice experiments (online or in the lab) confirmed that the higher color contrast image within a pair was preferred (regardless of whether the image was an original painting or not). Eye tracking revealed that images with relatively higher contrast captured attention. We conclude that previous reports of a preference for the original artworks may have reflected reductions in color contrast of the color-rotated alternatives. These findings point to color contrast as a potential esthetic primitive feature but at the same time cast some doubts on relying exclusively on the results of forced choice tests for revealing genuine esthetic preferences.