Left-handers' smiles: asymmetries in the projection of a posed expression.
Asymmetries in the expression of a posed smile and in a relaxed facial expression were observed in 24 left-handers. Neither writing position nor familial sinistrality predicted the variance of the results. Left-handers were found to smile more with their left than right side of face; an asymmetry which had previously been observed in right-handers. If anything, left-handers' smiles were more asymmetric, though in the same direction, than right-handers. When relaxed, however, the left-handers' face was judged more unhappy on its right than left side--a reversal of the direction of asymmetry previously noted in right-handers' relaxed expressions. No single neurological or psychological theory accounts for these results; it is suggested that hand preference may exert a myotonic effect which is reflected in judgements of relaxed facial expressions.
D000293:Adolescent; D000328:Adult; D001931:Brain Mapping; D004292:Dominance, Cerebral / Q000502:physiology*; D005149:Facial Expression; D005260:Female; D007839:Functional Laterality; D006801:Humans; D008297:Male; D008875:Middle Aged; D012904:Smiling; D014796:Visual Perception