- Targets under separate lighting conditions have been shown to exhibit either the color spreading effect or the illusory contour effect.
- Ratliff, who taught at Rockefeller for 31 years and became a professor emeritus in 1989, also studied the relations binding the visual arts and visual sciences as witnessed in 19th-century science, Neo-Impressionism and the contrast and contour effects of art of the Sung Dynasty.
- During the 1940s he began the laborious task of mapping the marginal features of the Moon . ( That is, the features that would produce a contour effect along the limb due to libration . ) This study was based upon roughly 700 photographs of the lunar limb taken between 1927 up until 1956.