Figure 4.

Diagram illustrating Smilek et al. method. In the experiment by Smilek and colleagues, they showed black shapes (that appeared colored to the synesthetes by virtue of their condition) on different colored backgrounds. The detection of the shapes was more accurate when the color that the shapes appeared was different from the background. This figure demonstrates this effect. Here, a black 7 appears red because of the synesthetic perception. On a red background, this 7 is obscured, but on a blue background, the 7 is more visible.