Scientists at the University of Haifa in Israel have concluded that at least some of a person's facial expressions are genetically determined. They came to this conclusion after interviewing 21 blind volunteers and comparing their facial movements with those of 30 sighted relatives.
The subjects, all blind from birth, would not have been able to mimic their relatives' movements, suggesting that shared facial expressions would have arisen innately.Next they'll be testing the if-you-keep-making-that-face-it'll-stay-that-way hypothesis I first heard posed by my mother when I was six.
Volunteers were asked to relate experiences that involved sadness, anger and joy. Other emotions like concentration, disgust and surprise were elicited by other methods.
The researchers found that significantly more of the blind volunteers' facial movements involving concentration, sadness and anger matched a family member's expressions than those of a stranger. [Link]