Tuesday, July 22, 2008

Evolution of Facial Expressions

A forlorn evolutionary biologist walks into a bar, and the bartender asks "why the long face?". "Because it helps alter my sensory interface with the physical world" replies the biologist.

The latest issue of Nature Neuroscience has a fascinating article entitled "Expressing fear enhances sensory acquisition" by Joshua Susskind et. al. Here is the abstract:

It has been proposed that facial expression production originates in sensory regulation. Here we demonstrate that facial expressions of fear are configured to enhance sensory acquisition. A statistical model of expression appearance revealed that fear and disgust expressions have opposite shape and surface reflectance features. We hypothesized that this reflects a fundamental antagonism serving to augment versus diminish sensory exposure. In keeping with this hypothesis, when subjects posed expressions of fear, they had a subjectively larger visual field, faster eye movements during target localization and an increase in nasal volume and air velocity during inspiration. The opposite pattern was found for disgust. Fear may therefore work to enhance perception, whereas disgust dampens it. These convergent results provide support for the Darwinian hypothesis that facial expressions are not arbitrary configurations for social communication, but rather, expressions may have originated in altering the sensory interface with the physical world.