Beauty is in the ease of the beholding: a neurophysiological test of the averageness theory of facial attractiveness.

Hundreds of studies have shown that people prefer attractive over unattractive faces. But what is an attractive face, and why is it preferred? Averageness theory claims that faces are perceived as being attractive when their facial configuration approximates the mathematical average facial configuration of the population. Conversely, faces that deviate from this average configuration are perceived as being unattractive. The theory predicts that both attractive and mathematically averaged faces should be processed more fluently than unattractive faces, whereas the averaged faces should be processed marginally more fluently than the attractive faces. We compared neurocognitive and behavioral responses to attractive, unattractive, and averaged human faces to test these predictions. We recorded event-related potentials (ERPs) and reaction times (RTs) from 48 adults while they discriminated between human and chimpanzee faces. The participants categorized averaged and high-attractive faces as being "human" faster than low-attractive faces. The posterior N170 (150-225 ms) face-evoked ERP component was smaller in response to high-attractive and averaged faces than to low-attractive faces. Single-trial electroencephalographic analysis indicated that this reduced ERP response arose from the engagement of fewer neural resources, and not from a change in the temporal consistency of how those resources were engaged. These findings provide novel evidence that faces are perceived as being attractive when they approximate a facial configuration close to the population average, and they suggest that processing fluency underlies preferences for attractive faces.