The Origins of Face Processing in Humans and Ontogeny

ABSTRACT— Faces are crucial for nonverbal communica-tioninhumansandrelatedspecies.Fromthefirstmomentsoflife,newborninfantsprefertolookathumanfacesoveralmostanyotherformofstimuli.Sincethisfindingwasfirstobserved, there has been much debate regarding the‘‘special’’natureoffaceprocessing.Researchershaveputforward numerous developmental models that attempt toaccount for this early preference and subsequent matu-ration of the face processing system. In this article, wereview these models and their supporting evidence draw-ing on literature from developmental, evolutionary, andcomparative psychology. We conclude that convergingdata from these fields strongly suggests that face process-ing is conducted by a dedicated and complex neural sys-tem,isnothumanspecific,andisunlikelytohaveemergedrecently in evolutionary history.Indisputably, humans are a social species. From the very firstmoments of life, newborn infants demand near constant mater-nal care and attention during their waking hours. This veryspecial form of socialization represents the advent of our in-duction into life as a social organism. Throughout ontogeny, wesocially interact with perhaps thousands of other individuals.Our ability to perform this function successfully hinges on ourcapacity to reliably convey our internal emotional state to con-specifics and understand theirs in return. Central to this com-municative process is the human face.Thefacesofourhumanconspecificsareubiquitouswithinthevisual environment. Indeed, face processing researchers oftenclaimthathumansspendmoretimelookingathumanfacesthanany other category of complex visual stimuli. To the best of ourknowledge, this is an assertive observation rather than a state-ment of fact. However, few people would challenge the legiti-macy of such a notion, and it is certainly one that we readilyendorse. As a consequence of this immeasurable and unparal-leledexposure,adultsseeminglypossessan extraordinarylevelof competence in the domain of face processing. It is this pro-ficiency that lies at the heart of a debate that is endemic withinthe face processing literature: Does face processing hold a un-ique status within the brain?In this review, we will argue that the answer to this questionis an emphatic ‘‘yes’’ and that the evidence to support thisconclusion is overwhelming. In particular, we will draw ondevelopmental, evolutionary, and comparative psychology todemonstratethatfaceprocessinginhumansandrelatedspeciesisperformedbyadistributedcognitivesystemthatisunlikelytohave evolved recently in evolutionary history and is pivotal forour ability to function as a social species.