Fear: What is it Good For? Fuzzy Logic!

FEAR changes how we see things, enhancing our ability to identify blurry shapes but impairing our perception of fine details. This may help us to escape threats.

Looking at a fearful face, which activates the brain in a similar way to feeling fear, enhances sensitivity to visual contrast, but whether it improves vision across the board wasn't clear. So Bruno Bocanegra and René Zeelenberg at Erasmus University in Rotterdam, the Netherlands, showed people pictures of faces with either fearful or neutral expressions, followed by a "blob" covered in stripes of varying thicknesses.

Those shown a fearful face were better at identifying whether thick stripes were vertical or slightly tilted and worse at identifying the orientation of thin stripes than those shown neutral faces (Psychological Science, DOI: 10.1111/j.1467-9280.2009.02354.x).

This response may have evolved because coarse-grained features, which enable you to evaluate movement and distance, better aid survival in scary situations than fine details. "You don't care whether the object has wrinkles, you care whether its movement is threatening," Bocanegra says.