The asymmetrical status of facial beauty has rarely been investigated. We studied positive facial characteristics, attractiveness and smiling, through the use of left-left and right-right composites of unfamiliar faces of women and men with natural expressions. Results showed that women's right-right composites were judged significantly more attractive than left-left composites while there was no left-right difference in men's composites (Experiment 1). On the other hand, left-left composites were judged to have more pronounced smiling expressions than right-right composites in both women's and men's faces (Experiment 2). The results confirm previous findings for leftward facial expressiveness and show for the first time asymmetry in facial attractiveness and a difference in its manifestation in women's and men's faces. The findings have biological implications for the relationship between the appearance of the sides of the face and hemispheric specialization. The organization of beauty in the human face may have been shaped by evolutionary pressures on facial asymmetries, especially as they pertain to mate selection.

Abstract*We recently reported _nding asymmetry in the appearance of beauty on the face ðZaidel et al [\ Neuropsycholo`ia\ Vol[ 22\ pp[ 538Ð544\ 0884Ł[ Here\ we investigated whether facial beauty is a stable characteristic "on the owner|s very face# or is in the perceptual space of the observer[ We call the question {the owner vs observer hypothesis|[ We compared identity judgements and attractiveness ratings of observers[ Subjects viewed leftÐleft and rightÐright composites of faces and decided which most resembled the normal face "Experiment 0#[ Identity judgements "resemblance# are known to be associated with perceptual factors in the observer[ Another group viewed the same normal faces and rated them on attractiveness "Experiment 1# viewing conditions# could re~ect "0# the facial halves of 12\ 28Ł and\ to a lesser extent\ in identity "resemblance the owner perceived in the left or right visual spaces judgements# ð2\ 07\ 25Ł[ Asymmetric aspects of facial "projecting via anatomical pathways to the right and left beauty have largely been neglected[ Yet\ physical facial hemispheres\ respectively# of the observer\ or "1# features attractiveness has some biological signi_cance ð5\ 6\ 14\ inherent in the physiognomy of the owner|s face[ In our 15\ 20\ 21\ 22Ł\ and its assessment must be anchored in previous study ð28Ł\ in women|s faces\ there was a sig! neuroanatomy[ We recently reported _nding functional ni_cant di}erence between LF and RF\ with the RF asymmetry in facial beauty and a di}erence in its man! judged more attractive than the LF "by both female and isfestation on women|s and men|s faces\ in head!on male observers#[ In men|s faces\ there was no leftÐright photographs ð28Ł and in painted _ne!art portraits ð27Ł[ di}erence[ The stimuli were leftÐleft and rightÐright com! However\ there has always been a question regarding posites of normal faces prepared from a facial half and facial asymmetry] {Is the asymmetry perceptual or is it in its mirror re~ection[ On the whole\ the bulk of neu! the physiognomy of the face of the observed "the ropsychological studies associate expressions with LF\ owner#<|[ We shall refer to this question as the {observer while identity is associated with RF[ In the present study\ vs owner hypothesis|[ "Hereafter\ left or right of the our goal was to compare the observer vs owner hypoth! owner|s face refers to the owner|s body\ e[g[ the left side esis in facial attractiveness and identity[ of the owner|s face is ipsilateral to the owner|s left hand\ Evidence for facial asymmetry in the size of soft!tissue ð05Ł would imply asymmetry in neuroanatomical control as well as in the organization of beauty on the sides of