Asymmetry of facial expression related to handedness, footedness, and eyedness: a quantitative study.

This study investigates the relationship between traditional measures of lateral dominance and facial asymmetry or facedness, i.e., the relative intensity of expression "and muscular involvement" on the two sides of the face. Subjects were 19 left-handed and 29 right-handed normal adults coached to produce eight facial expressions of emotion and one expression involving unilateral facial movement. Videotapes of each subject were reliably rated for facedness. A lateral dominance battery yielded preference scores for hand, foot, and eye, and performance scores for accuracy, speed, and strength. Facedness and lateral dominance scores were intercorrelated. For all subjects, facedness for the eight emotional expressions was positively related to eyedness, but unrelated to handedness or footedness. Facial asymmetry during emotional expression was more intense on the left side of the lower face and may be a right hemisphere function, regardless of handedness. The one expression requiring deliberate unilateral facial movement was significantly and inversely related to handedness and footedness.