Take a look at these two faces.
One of these women can’t recognize that the other is afraid, but when asked to express fear, is still able to produce a fearful expression. Can you tell which is which?
We know the amygdala is associated with identifying scary music; we know the amygdala helps us generate a fear response, but what about producing a fear response?
S.P. are the initials of a 54-year-old woman who had surgery to remove her right amygdala to alleviate the symptoms of epilepsy. During the surgery, it was found that her left amygdala was damaged as well, and so she effectively lost the function of the entire amygdala. The amygdala is primarily associated with processing the emotion of fear, so it was to be expected that S.P. would not be able to recognize fearful facial expressions. What had not been previously studied, however, is whether she would be able to produce the same expressions.
Adam Anderson and Elizabeth Phelps showed S.P. faces corresponding to each of six different emotions: happy, surprised, afraid, angry, disgusted, and sad. She rated each face on a scale of 1 to 6 for how well the face expressed each of the six emotions. A group of 20 normal volunteers also rated the same faces. Here’s how the responses broke down for the all-important fear rating:
S.P.’s ratings weren’t significantly different from normal individuales except in one case: when the face depicted fear. Then her ratings were significantly lower than the others. One month later, the experimenters asked S.P. to perform another task: they had her think of a situation which inspired each of the six emotions. Then she was asked to show what the facial expression for that emotion would look like. (The normal volunteers did this task immediately after performing the emotion identification task.) Finally, a set of three judges rated photos of all the participants for how well they expressed the intended emotion. Here are the results:
For each of the intended emotions, S.P. was able to express them at least as well as the normal volunteers, and for the key emotion of fear, S.P. was in the 85th percentile.
Anderson and Phelps conclude that while the amygdala may be responsible for the perception of fear, the production of fearful facial expressions must be produced elsewhere in the brain. Further tests showed that S.P. was capable of understanding the situations which may produce fear — her primary impairment was simply the recognition of fearful facial expressions.
So, can you guess which of the faces depicted above was S.P.’s? Let us know in the comments.
Anderson, A.K., & Phelps, E.A. (2000). Expression without recognition: Contributions of the human amygdala to emotional communication. Psychological Science, 11(2), 106-110.