The amygdala's response to fearful facial expressions is automatic, and the ability to detect any sign of imminent danger in the environment is of equal importance to all people. Some have therefore argued that the amygdala's response to fearful facial expressions will not affected by culture. Others suggest that the amygdala's response will be enhanced for the fearful expressions of those from the same culture, because a threat to someone from the same cultural group might be a more pertinent signal of a threat to oneself.
Chiao and her colleagues now find evidence for the latter hypothesis.
This is beautiful science. As I described in a profile in Scientific American Mind, Joe LeDoux long ago (well, over the past 30 years) used rat studies to establish the amydala as the "fear center" -- and he did so with a completeness that makes it natural to think of the amygdala as a sort of evolutionary absolute that expresses itself consistently across context. Our seemingly "instinctive" fearful reactions to stimuli such as fearful faces can seem so hard-wired as to be immune to culture. (Note we're talking about fears that are so deeply embedded in evolutionary history that we consider them instinctive; these aren't, in other words, learned responses._ As Mo points out, this study suggests that even such instinctive reactions can be shaped in subtle ways by culture.
The authors of the new study suggest that the brain's response to fear is modulated by culture itself. Being born into, and spending one's life within, a certain culture inevitably leads to exposure to a common but unique set of social practices, values, beliefs and experiences. This may therefore fine-tune the amygdala so that it is sensitive to, and optimally activated by subtle variations in facial expressions that are specific to that culture.