race brain & behavior

Over the past decade, there have been unprecedented advances to the understanding of the human brain.  There has been some really exciting research with neuroimaging that gives us a glimpse window of the brain activity underlying complex human behaviors. Using neuroimaging techniques, recent studies have begun to explore the brain systems involved in behaviors we consider to define individuals, such as moral reasoning(e.g., Greene, Sommerville, Nystrom, Darly, & cohen, 2001), social cooperation (Rilling et al., 2002), violent tendencies (Davidson, Putnam, & Larson, 2000), responses to race groups (e.g., Phelpset al., 2000) and love (e.g., Bartles & Zeki, 2000). From a scientific perspective, these research tools provide additional routes to help us understand these complicated and important behaviors. However, whether this knowledge has any significance beyond furthering basic behavioral and neural science remains unclear.

                Even though brain science cannot help us predict human behavior, nor can we use it to help guide our social and political choices, we can start to uncover the neural basis of behaviors that are relevant to our social and political lives, to improve our understanding of complex human behaviors. To explore this to topic, in the novel Race, Brain and Behavior, Phelps and Thomas review what has been learned about the neural basis of social group processing, in particular social groups defined by race.

There have been two major findings concerning our understanding of the neural processing of race group information. The first is related to our ability to recognize faces from our won and other race groups. Psychological research has shown that we have a tendency to recognize faces of our own race more quickly and accurately than faces of another race: This is called the same-race advantage. (Brigham & Barkowitz, 1978; Brigham & Malpass, 1986; Chance & Goldstein, 1996; Malpass & Kravitz, 1969). This may be due to the contact hypothesis, which attributes this enhanced recognition to greater experience with faces of our own race. This hypothesis is supported by studies showing that the same-race advantage is greater for White than for Black Americans. It is proposed that because black Americans are a minority in the US, they are more likely to come into contact with other race groups other than White Americans, who are in the majority (Brigham & Malpass, 1986; Carroo, 1986; Fallshore & Schooler, 1995; Malpass & Kravitz, 1969).

                Neuroimaging data and studies in patients with specific brain injuries have identified an area in the brain that specializes in face recognition(Haxby et al., 1994; Kanwisher, McDermott, & Chun, 1997; Puce, Allison, Gore, & McCarthy, 1995). This region, the fusiform gyrus, is commonly called the fusiform face area(FFA). In an effort to determine whether the same-race advantage can be detected in this brain region, GGC&E(2001) used fMRI. Ten black and ten White American subjects were shown pictures of unfamiliar black and white faces, along with pictures of objects. They were asked tor remember what they saw and was later tested for their ability to remember the stimuli. This test yielded a same-race advantage, consistent with previous studies. Both black and white subjects were better at recognizing same-race faces, but this was a significant effect only for the white subjects who demonstrated a relatively larger same-race advantage.

The imaging data from this study showed that there was greater activation of the FFA when subjects viewed same-race versus other-race faces. This difference was apparent in both the black and white subjects, primarily in the right fusiform gyrus. Previous studies have found the FFA to be primarily localized in the right hemisphere (e.g., Kanwisher, 2000). Golby et al. (2001) . Golby et al. (2001) also conducted a correlation across subjects in which they compared the magnitude of the FFA response to same-race versus other-race faces was significantly correlated with greater activation of the left fusiform gyrus as well as the right hippocampal and parahippocampal gyri, regions known to be important for memory in general (Cohen & Eichenbaum, 1993). They pro-posed that face processing is asymmetric, with the left hemisphere mediating cat-egorical visual processes (i.e., black vs. white) and the right hemisphere mediating processes involved in individuating faces within a category.             

                Golby et al. (2001) suggested that the differences in FFA recruitment for same-race versus other-race faces could be due to long-term differences in experience with members of these race groups as well as the attentional processes that emphasize classifying other-race faces with the use of race-specific information(categorical, left hemisphere) rather than individuating information (right hemisphere).

This study is interesting because it links neural basis of face recognition with the recognition of race group information. This can help us to understand how individuals of different races are represented in the brain and advances our understanding of the role of the FFA and extends it to the processing of race group information. However, these results do not explain the behavior of recognizing same-race versus other-race faces that we obtained from previous research. We already knew that this advantage is more prominent in white rather than black Americans, and varies across individuals. Knowing how this behavior is represented in the brain does not change these facts.

Although this study is an important first step, some aspects of the role of FFA in the same-race advantage remain unresolved. For instance the role of the left fusiform gyrus in the recognition of faces is not clear. Most previous studies examining the FFA have reported a right hemisphere advantage. Moreover, the Golby et al. data do not entirely support the link between the same-race advantage and the FFA response. In this study the White American subjects showed a greater same-race advantage, consistent with previous results. However, the black American subjects showed a more consistent FFA response to same-race versus other-race faces. About 75% of white subjects showed greater FFA activation to same-race faces in comparison to all of the black subjects, including those black subjects who did not show any race-related recognition bias. These questions point to potential problems in determining the precise link between the FFA and the same race advantage that will need to be addressed later.

The second main finding that has emerged concerns biases in the evaluation of individuals on the basis of race group membership. These studies have focused on a brain region called the amygdale. The amygdal has been shown to be important for emotional learning and memory specifically the “expression of a learned evaluation when assessed indirectly, such as through a physiological response”(e.g., LeDoux, 1996). Specifically, the amygdale has been shown to be important for the expression of a learned evaluation when it is assessed indirectly, such as through a physiological response.

The evaluation of social groups defined by race is a truly important topic that has been studied by social psychologists for decades. Studies show that there has been a consistent decrease over the years in the explicit report of negative attitudes toward black Americans expressed by White Americans( ). However, there is significant evidence that when attitudes are assessed indirectly or implicitly, most white Americans demonstrate a negative bias toward Black Americans(Banaji, 2001; Blargh&Chen, 1997; Devine, 1989; Fazio, Jakcson, Dunton, & Williams, 1995; Fiske, 1998; Nosek; Banaji, & Greewald, 2002). There are a few possible reasons for this observed dissociation between an implicit negative bias and an explicit unbiased report. One is that this negative implicit bias is consistent with a biased explicit attitude, but subjects are simply reluctant to admit a biased attitude. However, it is also possible that even those subjects who consciously believe that there is no reason for a biased attitude are influenced by cultural stereotypes and limited experiences, in such a way that biases are implicit that are not subject to conscious control and mediation and is something that occurs “unconsciously” and “unknowingly”(Birgeneau, 1999).

In order to determine whether the dissociation in the neural systems underlying implicit and explicit assessments of evaluation could be linked to the dissociation observed among white Americans in explicit and implicit measures of race bias, (Phelps et al, 2000), used fMRI to examine the relationship between activation of the amygdale and behavioral measures of race bias. During brain imaging, white American subjects were shown pictures of unfamiliar black and white male faces. They were simply asked to indicate when a face was repeated. After imaging, subjects were given a standard explicit assessment of race attitudes and two indirect assessments of race bias. The first indirect test measured startle potentation while viewing the same faces. Startle is a reflex that is potentiated in the presence of stimuli considered to be negative(Grillon, Ameli, Woods, Merikanguys, & Davis, 1991; Lang, Bradley, & Cuthbert, 1990);  the difference in the magnitude of the startle reflex in the presence of the black versus white faces served as the indirect measure of bias. The second indirect measure of bias was the Implicit Association Test( ). In this study, the IAT involved the presentation of a series of trials on which a black or white unfamiliar face was presented; subjects were asked to classify these faces according to race as quickly as possible.

The behavioral results from this study (Phelps et al, 2000) mirrored those of previous studies (see Banaji, 2001). The White American subjects showed a relatively pro- bias as measured by the explicit test, the MRS, while at the same time they exhibited an anti-black bias as measured indirectly by the IAT. On the startle potentation test, they showed a nonsignificant trend toward greater startle while viewing black versus white unfamiliar faces. The imaging results did not yield a main effect for race. Although the majority of these subjects showed greater amygdala activation to the black faces than to the white faces, this effect was not observed in all of the subjects. When the variability in amygdale activation to black versus white faces across subjects was correlated with the variability in the behavioral measures, an interesting pattern emerged: those subjects who showed greater negative bias on the indirect measures of race evaluation (IAT and startle) also showed greater amygdale activation to the black faces than to the white faces. This shows that the amygdala response was predictive of race bias evaluation when this bias was measured indirectly, but not explicitly.

This study is serves as an important link to what is known about the neural systems of emotional learning and evaluation to the evaluation of social groups because it relates social evaluations to the ordinary mechanisms of everyday emotional learning and memory. Also, by showing a brain region whose activation response is correlated with indirect but not direct measures of evaluation, this study supports the idea that attitudes toward social groups can be expressed both directly and indirectly and that these two means of expression may represent different underlying processes. However, like the study with face recognition mentioned earlier, it is unclear what we have learned about the behavior of race bias that we did not already know.  We may infer from these neuroimaging results that we are able to detect biases that individuals are unwilling to admit, but as this study indicates, behavioral tests are already able to detect such biases. Indeed, the only real way we can understand the behavioral significance of this or any other brain activation result is by linking it to behaviors we have defined. In addition, there are several other factors to consider when interpreting these results.

First, how general are these results? The subjects in the study by Phelps et al. (2000) were White Americans. Would individuals from other race groups display similar behavior? Overall, Black Americans show more variability than White Americans on measures of indirect race bias, with some showing a pro-black bias and other showing no bias or a pro-white bias(Nosek et al., 2002). If amygdala activation to some-race versus other-race faces predicts a negative bias on indirect measures of race-evaluation, we might expect a less consistent amygdale response to same-race versus other-race faces in black American subjects. However, a study by Hart et al. (2000) observed greater amygdala activation to other-race faces than to same-race faces in both groups. In this study, the activation response was not linked to behavioral measures of race evaluation, making it difficult to know whether this link between implicit race bias and amygdale activation extends to black American subjects.

Second, does this effect extend to other stimuli that vary by race? Both the Hart et al. (2000) and Phelps et al. (2000) studies presented photographs of unfamiliar black and white male faces. A previous study(DuBois et al., 1999) reported that the amygdale shows increased activation to unfamiliar versus familiar neutral faces. Could it be that the amygdale response to same-race versus other-race faces is driven by greater familiarity with one’s own race group? How might the responses observed in these studies be changed by familiarity? In an effort to address this question, Phelps et al. (2000) conducted a second study in which the faces presented belonged to familiar black and white male individuals. In this study, the white American subjects did not show any consistent evidence of stronger amygdale activation to the black versus white faces. The indirect startle test also failed to show any differentiation between race groups. Although the IAT, bias toward black faces, performance on this task was not correlated with an amygdale response. This second study suggests that this amygdale response can be modified by experience and familiarity.

Finally, what does an “activation” response measured with fMRI tell us about the precise role of the amygala in this study? Brain activation is usually measured in response to a mental challenge created by the experimenter. In the Phelps et al. study, pictures of faces were presented during brain imaging and subjects were asked to respond to the identity of the individual faces, but clearly subjects also coded race group information from these stimuli. The result was a relationship observed between the differential amygdale response to the race groups and indirect measures of race bias. This relationship or correlation between the brain response and the behavioral measures does not tell us how or if the amygdala is involved in generating these behaviors; it indicates simply that there is some relationship. An activation response does not inform us as to what, exactly, a brain region does in the generation of a behavior. To determine the precise role of a given brain region in a task, we must use other techniques. Combining the psychological and neural approaches is the best way to advance our understanding of these complex human behaviors more rapidly and with more clarity than could be achieved using either approac02h in isolation.

These results really highlight how neural science can contribute to psychological science. Studies examining how the brain processes race information have provided support for psychological theories concerning the same-race advantage for recognition and the dissociation between direct and indirect measures of race group evaluation. As these studies indicate, a good understanding of the potential contributions of brain imaging can help us discover the structure and organization of a behavior. However, a partial understanding can lead us to conclusions that are inconclusive and misleading. As we develop techniques that allows us to investigate the biological basis of complex behavior, we need to be clear about what it means to say that a behavior is “in the brain.”

Moreover, showing a behavior “in the brain” does not indicate that it is innate, “hard-wired”, or unchangeable. Every experience leads to an alteration in the brain. Some of these alterations may be long-lasting and result in learning or memory. For example the second study by Phelps et. Al. (2000) showed that the amygdale response to same-race versus other-race faces can be altered by familiarity and learning. Although it is often exciting to demonstrate a neural basis for a given behavior, it should not be surprising to show that any behavior has an identifiable neural substrate. We all change, learn, and grow over time. It is easy to recognize the dynamic nature of behavior. Most of us also recognize the interdependence of behavior and the brain. We all have heard of or know someone who has suffered a brain injury resulting in a change in behavior. However, it is somehow more difficult to make the additional connection and recognize the dynamic nature of the brain. Changes in behavior correspond with changes in brain activity and structure. Discovering the representation of a behavior in the brain does not discount the influence of learning in generating, maintaining, or changing this behavior.

Furthermore, showing a behavior “in the brain” does not say something more important or fundamental about who we are than our behavior. Functional neuroimaging techniques pick up on signals indicating brian activity. These signals, by themselves, do not specify a behavior. Only by linking these brain signals with behavior do they have psychological meaning. For example, recent research has shown different brain activity patterns doing reading in individuals with dyslexia(e.g. Habib, 2000). Discovering the brain activity related to this disorder does not change the defining characteristic of dyslexia, which is difficulty in reading. We would not label someone “dyslexic” solely on the basis of his or her brain activity pattern; likewise, we should not label someone “racist” because of the pattern of his or her brain response. Assessing brain activity may aid our understanding of a behavior, but the psychological meaning of these brain signals comes from their link to behavior. Discovering the brain activation pattern linked to a behavior does not change the importance of that behavior. It is also unlikely to tell us something about ourselves that we could not conclude from the behavior itself.

Despite these misconceptions, these maps of brain activation patterns are compelling demonstrations of our newfound ability to investigate the biology of human behavior. For neuroscientists, it is an exciting time to try to unravel the complex circuits that tie together the brain and behavior. However, we need to be reasonable in our interpretation of this research and use it to enhance, not subtract from, other means of investigation. These advances in neuroscience should not negate nor substitute for advances in the psychological understanding of behavior.

References

Race, Behavior, and the Brain: The Role of Neuroimaging in Understanding Complex Social Behaviors, by Elizabeth A. Phelps and Laura A. Thomas Political Psychology .  2003 International Society of Political Psychology.