Brain's response to fear is culture-specific

In The Expression of the Emotions in Man and Animals, Charles Darwin noted that facial expressions vary little across cultures. We all recognize that someone whose eyes and mouth are wide open, and whose eyebrows are raised, is afraid. This characteristic expression is a social signal, which warns others of a potential threat and serves as a plea for help. It also enhances our ability to sense potential threats, by increasing the range of vision and enhancing the sense of smell.    

Recognizing fear in others involves perceiving cues which we are consciously aware of as well as subliminal cues. But the brain's response to fearful facial expressions is automatic, so one might assume that it is universal. However, a collaborative study by American and Japanese researchers, published in the December issue of the Journal of Cognitive Neuroscience, provides evidence that the neural response to fear is fine-tuned by culture.

The new study was led by Joan Chiao of the Social and Cultural Neuroscience Lab at Northwestern University. 22 volunteers were recruited for the study; 10 were Caucasians living in the United States, and the remaining 12 were native Japanese living in Japan. All the participants were presented with a series of pictures of 80 faces, each for 1.5 seconds, and each depicting an American or a Japanese person expressing either a fearful, happy, angry or neutral facial expression. Their neural responses to the facial expressions in the pictures were measured using functional neuroimaging. 

The researchers measured activity in the amygdala, an almond-shaped structure located in the medial temporal lobe. The function of the amygdala has been studied intensively, and it is now well established that this part of the brain is critical for the recognition of emotions in others. The amygdala is continuous with the anterior (front) of the hippocampus, and plays an important role in the formation of fearful memories. Previous studies have examined activation of the amygdala in response to emotional facial stimuli, but these have been carried out in either the U.S. or Western Europe, and none has explored cross-cutural differences these responses.

The amygdala's response to the fearful facial expressions of others is culture-specific

(From Chiao et al 2008).

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 be 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. All of the participants involved in the study were tested in their home country by researchers who conducted the study in their native language - the American participants were scanned at the Athinoula Martinos Center for Biomedical Imaging at Massachusetts General hospital, and the Japanese participants at the National Institute for Physiologal Sciences in Osaka. Both neuroimaging facilities used the same make and model of fMRI machine, and the quality of the signals obtained from both was found to be comparable. 

Both groups of participants could recognize the emotions depicted in the pictures very accurately. Interestingly though, the Japanese participants were significantly quicker in recognizing fear in all the pictures, while the Americans were significantly more accurate at recognizing fear in pictures of people from their own culture. More importantly, the response of the amygdala was increased when the participants recognized fear in pictures of members of their own cultural group relative to others. Hemispheric differences were also observed: the increase in amygdala activity in response to fear recognition in own-culture faces was significantly greater in the right amygdala than in the left. By contrast, no significant differences in amygdala activity was observed when the participants viewed pictures of happy, angry or neutral expressions.   

Earlier neuroimaging studies have shown that white Americans show an increased response in the amygdala when presented, either consciously or unconsciously, with pictures of black Americans with neutral expressions. By contrast, no differences in the response to neutral faces of either cultural group were observed in this study, even though Americans often hold positive sterotypes of Asians. Thus, the earlier observations may have been due to cultural knowledge of the negative sterotypes about African-Americans, rather than negative stereotypes of members of other ethnic groups per se. This is supported by the finding in the earlier studies that black Americans also exhibit increased activity in the amygdala in response to pictures of black people with neutral expressions.

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. The enhanced response to fearful facial expressions in people from members of one's own cultural group may result in a propensity to direct behaviours such as co-operation and altruism towards them. 

Related:

• The smell of fear
• The neurobiology of fear
  

Chiao, J. Y. et al (2008). Cultural Specificity in Amygdala Response to Fear Faces. J. Cog. Neurosci. 20: 2167-2174.