NeuroReport - Press Release

Press Release
NeuroReport

Differential response in the human amygdala to racial outgroup vs ingroup face stimuli

Allen J. Hart, Paul J. Whalen, Lisa M. Shin, Sean C. McInerney, Håkan Fischer and Scott L. Rauch

Contact: Dr Paul J. Whalen, Dept. of Psychiatry, University of Wisconsin College of Medicine. Tel: +1 608 262 5127; email pwhalen@facstaff.wisc.edu

NeuroReport Volume 11, number 11, 2351-2355
(Free online on this site)

Embargo date: 26 July 2000

A collaborative brain imaging study conducted at Massachusetts General Hospital in Boston, Massachusetts suggests that activity in the amygdala region of the brain to human face stimuli is affected by the relationship between the race of a presented stimulus face and that of the subject.

Using functional magnetic resonance imaging (fMRI) of the brain, activity was measured in subjects who identified themselves as Black or White while they viewed pictures of Black and White individuals' faces. Across all subjects, greater activity was observed in the amygdala to outgroup faces (i.e., race of presented face is different than that of subject) when compared to ingroup faces (i.e. race of presented face is the same as that of the subject). Interestingly, amygdala response to outgroup faces was not different than that seen to ingroup faces during initial stimulus presentations. The difference between outgroup vs. ingroup faces emerged over time as amygdala responsiveness decreased more readily to ingroup faces with repeated presentations.

The authors chose to study Black and White subjects, though future studies could assess differences across a broader range of racial groups. This study was explicitly designed to assess fMRI responses to outgroup vs ingroup faces across subjects of both races, rather than to assess any differences that might exist between subjects based upon race.

The social psychology literature provides evidence that experimental subjects respond differently to face stimuli that depict members of their own race (ingroup) compared with those of a different race (outgroup). For example, subjects are better able to recognize previously presented ingroup faces compared to previously presented outgroup faces. Conversely, outgroup faces are more quickly classified by race than ingroup faces. These effects make it clear that the brain can fundamentally classify face stimuli by racial category and this categorization can affect a host of subsequent responses. Since the amygdala has demonstrated a propensity for response to face stimuli and its activity can modulate both perceptual and response pathways the authors sought to assess the effect that outgroup vs ingroup categories might have on amygdala response to faces of neutral expression. The authors reasoned that such information might impact the development of fMRI probes aimed at studying amygdala responses, since any representative cross-section of the population will be comprised of individuals from numerous racial groups.

The authors comment that while this line of inquiry has significant social implications, it is important not to draw premature conclusions. For example, future studies might seek to assess the relative contributions that each racial group (i.e., Black or White) makes to the amygdala response reported in this paper. Since outgroup stimuli differ for each experimental group, such studies will require stimuli that are carefully matched for variables other than racial category (e.g., degree of neutrality of expression between stimulus groups). In addition, whether the present effect will generalize to other racial groups is another important question for further study. Finally, perhaps the present results have implications for racial stereotyping. Indeed, the observed difference in habituation profile to outgroup stimuli is consistent with the notion that the amygdala might be sensitive to learned racial stereotypes or participate in their development. However, as noted by the authors, such an interpretation would have to account for the lack of difference observed during initial stimulus presentations.

An important implication of the present data for research in this domain is that the interaction between the race of subjects and face stimuli will contribute a significant source of variance, dictating that potential comparison groups be matched for race. Moreover, these initial findings, together with complementary efforts from independent laboratories may serve to stimulate future related neuroimaging studies into the neuroscience of social cognition and race.

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