Stabilizing and directional selection on facial paedomorphosis : Averageness or juvenilization?

Averageness is purportedly the result of stabilizing selection maintaining the population mean, whereas facial paedomorphosis is a product of directional selection driving the population mean towards an increasingly juvenile appearance. If selection is predominantly stabilizing, intermediate phenotypes reflect high genetic quality and mathematically average faces should be found attractive. If, on the other hand, directional selection is strong enough, extreme phenotypes reflect high genetic quality and juvenilized faces will be found attractive. To compare the effects of stabilizing and directional selection on facial paedomorphosis (juvenilization), graphic morphing and editing techniques were used to alter the appearance of composite faces to make them appear more or less juvenile. Both facial models and judges of attractiveness were from the CSU-Long Beach campus. Although effect sizes for both preferences were large, the effect for averageness was nearly twice that found for juvenilization, an indication that stabilizing selection influences preferences for facial paedomorphosis more so than directional selection in contemporary humans.