Top panel: Age-related changes in movement coupling between selected facial markers. Standard error bars represent across subject variation in each age group. Bottom panel: Age-related changes in the within variability in movement coupling. The CV values for ER3LL at all ages studied and for UL3LL at 7 months were very large (e.g., 11.5) and therefore not displayed. ER, right eyebrow; EL, left eyebrow; UL, upper lip; CR, right oral commissure; CL, left oral commissure; LL, lower lip; JR, chin.