The Macbeth effect is the tendency for people who have acted or thought in an immoral or unethical manner to want to clean themselves physically as a kind of surrogate for actual moral cleansing.
Researchers looking at this effect wondered about other interesting characteristics of moral psychology which led them to devising a test for implicit links between different colours and morality. For example, the colour black is commonly connected with evil and white with good, and the researchers wondered whether this would present itself. It did:
Psychologists have long known that if people are presented with, say, the word “blue” printed in a blue font, they will be able to state the colour of the font much faster than if the word “red” is printed in the same blue font.
The study conducted by Mr Sherman and Dr Clore presented words of moral goodness, like “virtuous” and “honesty”, and of badness, like “cheat” and “sin”, in either black or white fonts on a computer screen. As they report in Psychological Science, the two researchers found that when “good” words were presented in black it took the participants about 510 milliseconds to state the colour of the word. When these same words were presented in white it took roughly 480 milliseconds—a significant difference. A similar effect was seen with “bad” words. Responding to white ones took around 525 milliseconds, whereas black ones needed only about 500. These results are remarkably similar to those found when words are printed in colours that clash with their meaning.