Prejudice in the brain

Despite the great strides that have been made toward a more egalitarian society in the United States over the past 50 years, events like what occurred in Ferguson last month are a bleak reminder of the racial tensions that still exist here. Of course, the United States is not alone in this respect; throughout the world we can see abundant examples of strain between different races, as well as between any groups with dissimilar characteristics. In fact, it seems that the quickness with which we form a negative opinion about those who are not members of the same group as us may be characteristic of human nature in general, as its effects have been pervasive throughout history, and it persists even when we attempt fastidiously to stamp it out.

Indeed, it may be that our inclination towards prejudicial thinking has its roots in what was once an adaptive behavior. Some argue that our ancient hominid ancestors may have benefited from living in small groups, as this allowed for joint efforts in gathering and protecting resources. A logical offshoot of the development of group living would have been the emergence of skill in being able to tell members of your group apart from those who were not. It might have paid off to be wary of those who were not part of your group, as they would have been more likely to pose a threat. According to this evolutionary hypothesis, prejudice--which can be defined as an opinion of someone that is formed based on their group membership--may be the result of this strategy being so effective in the past. In essence, we may be saddled with the mindset of our evolutionary ancestors, which makes us more skeptical at first of anyone whom we see as "different" than us.

Prejudice and the amygdala

If prejudice is a deep-seated human behavior, it would not be surprising to find networks in the brain that are selectively activated when someone has xenophobic thoughts. One area of the brain that has been investigated in this context is the amygdala.

The amygdala is often associated with emotion, and is perhaps best known for its role in fear and the recognition of threats. If you were walking in the woods and saw a bear, your amygdalae would immediately become activated, helping to bring about a fear response that would encourage you to run away (or maybe cause you to freeze in place).

Several neuroimaging studies have looked at what happens in the brains of people when they see images of others outside of their racial group (e.g. white people looking at images of black faces). Some findings from these studies include: the amygdala is activated upon seeing such images, amygdala activation is correlated with xenophobic attitudes of the viewer, and amygdala activity in white people is higher when viewing black faces with darker skin tone.

Thus, the amygdala may serve as a threat-detection mechanism that is reflexively activated when we see an outsider. Perhaps because this has been adaptive in the past, it may act to put our brain on alert when someone outside of our racial group is near. In many societies today, however, where we are attempting to make racial divisions less distinct, this knee-jerk reaction seems to be counterproductive.

Prejudice and the insula

Another area of the brain that has been associated with prejudice in neuroimaging studies is the insula. The insula is also involved in processing emotional states, and has been linked to mediating feelings of social disapproval. For example, one study found that the insula and amygdala were activated in individuals while they viewed pictures of of people deemed to be social outcasts, such as homeless people or drug addicts. Because the insula is also activated when viewing pictures of people outside one's racial group, it has been hypothesized that the insula is involved in feelings of distaste that may arise when experiencing prejudicial thoughts.

Prejudice and the striatum

The striatum, a subcortical area thought to play an important role in reward processing, also has been implicated in prejudice--albeit in a very different way than the amygdala and insula. Activity in the striatum correlates with rewarding experiences, and neuroimaging studies have found that the striatum is also activated when looking at pictures of individuals from one's own racial group. When white participants were tested for implicit preferences (i.e. preferences they may not state or even be aware of, but that they still seem to possess) for people of their own race, activity in the striatum was stronger in response to white faces in those who scored higher on the test for implicit preferences.

Thus, there may be activity in the brain that reinforces our tendency toward prejudice in at least two ways: 1) we may be more likely to feel fear and aversion when seeing someone of another race, and 2) we may be more likely to experience positive emotions in response to seeing someone of our own race.

So, if there are structures in our brains that promote prejudice, does it mean attempts to reduce our prejudices--both individually and societally--are a lost cause? Of course not. Just as there are brain structures that may make us more likely to recognize differences, there are also structures (e.g. areas of the frontal cortex) that allow us to exert control over those potentially reflexive reactions.

It's possible that the recognition of deep-seated mechanisms for prejudice could help us to understand racism a little better. It could, for example, provide insight into why people in high-stress situations may be more likely to see things as divided down racial lines. For, if their brains are already inclined to see people of another race as more threatening and they are in a stressful situation, they may be quicker to identify someone of a different race as the threat.

However, the extent to which such innate responses to outsiders affects our behavior is still somewhat unclear, and the hypothesis that such responses are remnants of once-adaptive behavior is just that: a hypothesis. For practical purposes, it may not matter exactly what the basis of prejudicial thinking is, as we are certain it's a thought pattern that doesn't have much remaining value in today's world. However, being open to the idea that we have some inclinations toward prejudicial thinking may help us to be able to train people to more mindfully deal with high-stress interactions with people of another race. For, instead of pretending these prejudicial thoughts don't (or shouldn't) happen, it would allow us to focus more on ways to mitigate the damage that might occur when they do.

Amodio DM (2014). The neuroscience of prejudice and stereotyping. Nature reviews. Neuroscience PMID: 25186236

The neuroscience of self-control

In the 1960s, a psychologist at Stanford named Walter Mischel began a series of experiments exploring the dynamics of self-control in children. In one such experiment, Mischel gave preschoolers the choice between two outcomes, one of which was clearly preferable. For example, they were able to choose between 2 marshmallows and 1 marshmallow (the experiments became known as the Stanford marshmallow experiments for this reason).

But there was a catch. The experimenter would tell the children that he had to leave the room for a short period of time. In the best-known version of the experiment, the child was forced to sit in the room with the less appealing prize (e.g. just 1 marshmallow). However, the only way the child could get the two marshmallows is if she waited until the experimenter returned (about a 15-minute period) and did not eat the one marshmallow before that point.

The experiment was designed to measure delay of gratification. Would the child wait 15 minutes or would she give in and eat the marshmallow, knowing it meant she had to forego the ultimately more rewarding outcome of receiving two marshmallows? Mischel found, as would be expected, that there was a lot of variability in the capacity of children to delay their gratification to obtain a more valuable prize. Some ate the one marshmallow right away, not being able to subdue their desire for even a few minutes. About 1/3 of participants waited the entire 15 minutes to get the second marshmallow.

But the really interesting part about this experiment came when Mischel et al. followed up with these kids about 10 years later. They found that the kids who showed the most self-control as preschoolers were, in adolescence, rated by their parents to be more verbally fluent, attentive, competent, skillful, academically successful, socially adept, and better at dealing with frustration. What's even more interesting is that the amount of time the children were able to delay their gratification was correlated with their SAT scores. A number of other studies have since found associations between this early ability to delay gratification and later measures of intelligence, academic success, and even body mass index.

Neuroscience of self-control

It has been hypothesized that the ability to delay gratification is dependent on a push-pull relationship between the frontal cortex and the limbic system. The frontal cortex (and especially the prefrontal cortex) is frequently associated with planning and decision-making. Thus, it may be that this is the area of our brain that allows us to realize the value of being patient and waiting for a less immediate, but overall more satisfying, reward. Interestingly, in people who are addicted to drugs like methamphetamine or heroin, we tend to see reduced activity in the prefrontal cortex, suggesting that part of their difficulty in achieving abstinence might be due to a decreased ability to appreciate the value of a long-term reward like being drug-free.

When we consider a short- vs. long-term reward, however, another part of our brain becomes active as well. The limbic system, which contains several structures and is known for its involvement in emotional processing, is also activated. The limbic system is often implicated in "gut" responses to things, whether aversive or pleasurable. Thus, when we see or think about a valuable reward, the limbic system responds by pushing us to get it. The limbic system takes more of a primitive approach, telling us to chase after those things that feel good and avoid those that feel bad. It may be responsible for the impatience associated with short-term reward seeking.

Improving self-control

The ability to delay gratification is an important part of a healthy and satisfying life. It allows us to skip the fatty food to have a healthy snack, lets us stop after the first drink instead of having the second (and third, fourth, etc.), and encourages us to accomplish what we need to at work before opening up the web browser to peruse Facebook. Because it is such a valuable skill, researchers are interested in figuring out how we can improve it.

The research suggests that one important part of improving self-control is setting specific and realistic goals. Goals should be designed based on your internal motivation (in other words it should be something you--not somebody else--wants you to do), otherwise they tend to be less effective. It is most effective to set goals that are meant to be achieved within a certain time frame, as this allows you to monitor progress at specific intervals. Research suggests that just the act of setting a specific and attainable goal improves self-control.

The next step after setting a goal is to monitor your performance. It's important to pay attention to actions that conflict with achieving your goal. However, it's equally important to accept any deviations from the intended course of action as learning opportunities instead of looking at them as failures. Being compassionate about your slip-ups increases the probability that you will eventually reach your goal; this has been seen, for example, in studies of smokers and dieters.

Along the way, it can be helpful to develop specific behavior plans relating to your goal. Creating a schedule that determines when, where, and how you will exercise the behavior needed to reach your goal can help you actually follow through on that behavior. For example, deciding that you will run on the treadmill for 30 minutes right after work on Monday, Wednesday, and Friday is more effective than deciding you will use the treadmill a few times a week, but not determining when and for how long.

Although a propensity toward stronger or weaker self-control can be seen at a young age, research suggests that self-control is a skill that can be improved with practice. So, regardless of how inactive your prefrontal cortex might be in relation to your limbic system, and even if at preschool age you would have been more likely to eat the one marshmallow than wait 15 minutes for the second, with a little work and some good goal-setting anyone really can enact changes in their behavior.

Inzlicht, M., Legault, L., & Teper, R. (2014). Exploring the Mechanisms of Self-Control Improvement Current Directions in Psychological Science, 23 (4), 302-307 DOI: 10.1177/0963721414534256

Can psychopathy be treated?

Some psychological conditions receive a disproportionate amount of attention in popular media relative to how frequently they actually occur in the population. One of those is psychopathy, a personality disorder that is characterized by antisocial behavior, impulsivity, and a lack of empathy. Psychopaths may be charming on the surface but tend towards pathological deception and indifferent manipulation of other people. And they are more likely to have behavioral problems or be involved in criminal behavior.

This description portrays the psychopath as a societal parasite, leaving little role in a community for such an individual other than as part of the criminal justice system. This turns out to be the reality for many psychopaths, who are estimated to make up only 1% of the general population but between 15-25% of the incarcerated population. But, as our criminal justice system is supposed to be designed to rehabilitate criminals, there is an important question regarding psychopaths that has yet to be answered: can psychopathy be treated? There is not a clear-cut answer to this question, and you might find a differing of opinion even among experts.

Neuroscience of psychopathy

One argument sometimes used in support of the idea that psychopaths are not truly capable of being treated is that studies have found brain abnormalities in psychopaths that might be associated with their deviant behavior. This argument becomes less valid, however, when we consider that there are neurobiological aberrations that can be detected in the brains of sufferers of any disorder. Just because there are predisposing neurobiological aspects of a disorder does not mean the disorder is untreatable; if this were the case, the list of psychological disorders we could treat would arguably be empty.

Studies with psychopaths have identified a number of neurobiological features that might be linked to the disorder. For example, abnormalities in limbic system function have been observed in psychopaths. The anterior cingulate cortex, part of a network that is activated when we observe other people experiencing pain, is one limbic area that has been implicated. In psychopaths, activation of the anterior cingulate when seeing others in pain is muffled. This has been interpreted as being partly responsible for the psychopath's reduced capacity for empathy. Other limbic structures hypothesized to play a role in psychopathy include the amygdala, hippocampus, and striatum.

There are also structural abnormalities in the brains of psychopaths. For example, studies have found psychopaths to have a larger corpus callosum, asymmetrical hippocampi, and deformed amygdalae. The significance of these structural differences, however, is not yet very clear.

Effectiveness of rehabilitation in psychopaths

As indicated, however, just because behavior is based in neurobiology doesn't mean it is immutable. If that were the case, we might as well give up on trying to change anything about ourselves. A more important question is if the research suggests that psychopathic behavior becomes less so with rehabilitation.

Unfortunately, there is not a straightforward answer to that question. Some do report that treatment may be beneficial. For example, studies by Caldwell et al. (2006) and Skeem et al. (2002) both found improvements in psychopaths with treatment (measured by likelihood of recidivism). However, other studies have obtained less optimistic results, ranging from little improvement in psychopathy with treatment to treatment seeming to exacerbate psychopathic behavior. All of the studies on psychopathy treatment have limitations, however, and there is not a well-controlled experiment that we can point to and feel confident that it tells us if psychopathy is treatable.

Influence on sentencing

One of the reasons it is important to know if psychopaths can be rehabilitated is that this information would likely have a significant influence on sentencing, parole hearings, etc. A study published a few years ago found that simply giving a judge information about the biology of psychopathy could lead to a reduction in the sentencing of a diagnosed psychopath (compared to a judge not receiving that information), even though the information didn't indicate psychopathy was treatable (in fact it implied the opposite). However, with or without information about the associated biology, a diagnosis of psychopathy may still add years to a sentence, as judges are more likely to consider the convict a continued danger to society.

With some reliable data about treatment to point to, we might be able to either provide evidential support for those extended sentences or justification for reducing them if proper treatment were provided (depending on what the data indicated). Right now, however, the data we have on rehabilitation of psychopathy is somewhat muddled, with some studies indicating it is possible and other studies suggesting treatment could actually make things worse. Until we have a more definitive answer, we should be hesitant about assuming psychopathy is untreatable; at the same time we should be exploring controlled experiments that allow us to obtain a better understanding of the response of the psychopath to rehabilitation.

Polaschek, D. (2014). Adult Criminals With Psychopathy: Common Beliefs About Treatability and Change Have Little Empirical Support Current Directions in Psychological Science, 23 (4), 296-301 DOI: 10.1177/0963721414535211

Sex smells: pheromones in humans

Communicating with pheromones.

By the middle of the 20th century, biologists had become aware of a unique type of communication occurring among insects. The communication involved the secretion of substances that were similar to hormones in some ways, but also very different. While hormones are secreted into the bloodstream to elicit some reaction in the body, these newly identified substances exited the body and were used to elicit a reaction in a conspecific (another organism of the same species). They were given the name pheromones, from the Greek pherin (to transfer) and hormon (to excite).

Since that time, a number of pheromones have been identified in invertebrates and vertebrates alike. For example, when a honeybee hive is disturbed, guard bees produce a pheromone that alerts other bees in the hive; it encourages them to exit the hive and promotes aggressiveness. Beekeepers know all about this signal; they use smoke to calm an angry hive of bees because smoke inhibits receptors in bee antennae that detect the pheromone.

Pheromones that elicit a variety of behaviors have been identified in a number of species. Some pheromones, like those seen in bees, are used to call conspecifics together to attack or defend something, some aid in marking territory, and others leave trails that conspecifics can follow (to a stash of food, for example). Many pheromones also are associated with sex.

A large number of species, from microorganisms on up, release pheromones that play some role in mating. Some species of bacteria use pheromones to tell other bacteria to prepare to receive a transfer of genetic material in a very unromantic form of bacterial "sex" called conjugation. Even mammals, however, communicate with sex pheromones. Males of a number of species investigate the anogenital region of females with their nose, which contains a special pheromone-detector called the vomeronasal organ. Through exposure to pheromones, the male may be able to tell if the female is ovulating and will be receptive to his advances.

Although pheromones have been detected in many species, it has long been debated if they play any role in human communication. One reason that some have argued against an important role for pheromones in humans is that evidence suggests we don't have a functional vomeronasal organ. However, there do seem to be some examples of hidden chemical signaling between people.

Perhaps the best known putative pheromone mechanism in humans is the McClintock effect. The McClintock effect describes menstrual synchrony, which is when the menstrual cycles of women living in proximity to one another begin to synchronize, or start at around the same time. The effect was named after psychologist Martha McClintock, who hypothesized that pheromones were responsible for the synchronization.

The McClintock effect is controversial, and some argue that it isn't a real biological effect much less something caused by pheromones. But a number of other studies have also found indications of possible human pheromonal communication. From these studies, two steroids in particular have emerged as potential pheromones: androstadienone and estratetraenol.

Androstadienone, a metabolite of testosterone, is found in male semen and in secretions from the armpit area. Research has suggested it may promote physiological arousal in women, but not in heterosexual men. Estratetraenol, on the other hand, is an estrogen found in female urine. Estratetraenol has been found to affect autonomic arousal in men. Thus, some studies suggest (though this is still a controversial area) that androstadienone and estratetraenol are pheromones that contain some information detectable by the opposite sex.

A point-light walker used to demonstrate human gait.

A point-light walker used to demonstrate human gait.

A study to be published this month in Current Biology investigated information about gender that might be conveyed by these two putative pheromones. The investigators, Zhou et al., explored the effects of androstadienone and estratetraenol on the attribution of gender to point-light walkers (PLWs) displayed on a screen. PLWs are a collection of dots that represent human movement (see gif to the right). By changing settings, PLWs can adopt a more masculine or more feminine gait.

Zhou et al. exposed heterosexual and homosexual or bisexual men and women to either androstadienone, estratetraenol, or a control solution while viewing PLWs that displayed a spectrum of walking styles that ranged from a feminine gait to a masculine gait, with gender-neutral gaits falling in between the two. The participants, after watching the PLW walk very briefly, had to make a judgment as to whether the figure was masculine or feminine.

The researchers found that exposing heterosexual males to estratetraenol decreased the frequency of "male" responses, but it didn't affect ratings from heterosexual females. Exposing heterosexual females to androstadienone increased the frequency of "male" responses, but this didn't occur in heterosexual males. The results from the homosexual and bisexual groups were a little more ambiguous; estratetraenol didn't have an effect and androstadienone increased "male" responses in homosexual men but only to a gender-neutral PLW (and even then it was barely statistically significant).

Zhou et al. hypothesize that estratetraenol and androstadienone were biasing men and women, respectively, to discern the opposite sex in the movement of the PLWs. Thus, the authors argue that these substances convey information about masculinity and femininity. If true, what this means for everyday male-female interactions is unclear. The concentrations of the steroids that Zhou et al. used were much higher than you'd be exposed to just by standing next to someone on the subway.

So, there is much still to be learned about human pheromones. Even if androstadienone and estratetraenol are capable of communicating gender-specific information, their actual effect on human behavior today may be negligible. Thus, human pheromones may just be vestigial artifacts from our evolutionary history that we don't really have a use for anymore. On the other hand, there may be a complex system of communication occurring between people all the time that we are completely unaware of. And this system of communication could be shaping important decisions in your life, such as who you mate with, without your conscious realization.

Zhou, W., Yang, X., Chen, K., Cai, P., He, S., & Jiang, Y. (2014). Chemosensory Communication of Gender through Two Human Steroids in a Sexually Dimorphic Manner Current Biology DOI: 10.1016/j.cub.2014.03.035

Why do I procrastinate? I'll figure it out later


If you are a chronic procrastinator, you're not alone. Habitual procrastination plagues around 15-20% of adults and 50% of college students. For a chronic procrastinator, repeated failure to efficiently complete important tasks can lead to lower feelings of self-worth. In certain contexts, it can also result in very tangible penalties. For example, a survey in 2002 found that around 40% of American tax-payers procrastinated on their taxes, resulting in errors due to rushed filing that cost an average of $400 per procrastinator. More importantly, we tend to procrastinate when it comes to medical care (both preventive and therapeutic), which can involve very real costs to our well-being.

Why is the urge to procrastinate so strong? It sometimes seems that we are compelled to procrastinate by a force that is disproportionate to the small reward we may get from putting off a task we're not looking forward to. According to Gustavson et al., the authors of a study published last week in Psychological Science, a predisposition to procrastinate may have its roots in our genes.

Previous research has suggested a potential link between a tendency to procrastinate and an impulsive nature. Gustavson et al. explored this possible connection by observing the traits of procrastination and impulsivity in a group of 181 identical and 166 fraternal twins. Because identical twins share 100% of their genes and fraternal twins only share around 50% of their genes, if a trait is shared by identical twins more frequently than it is by fraternal twins, it suggests the trait has a significant genetic basis (for more on twin studies see this post).

The investigators reported a significant correlation between procrastination and impulsivity (r = .65). The group also reported that their genetic model determined that procrastination and impulsivity were perfectly correlated (r = 1.0), suggesting that the genetic influences on procrastination and impulsivity might be completely shared. In other words, according to this study, there are no genetic influences on procrastination that aren't also affecting impulsivity.

But why would these two traits be associated with one another? Procrastination involves putting things off, while impulsivity involves doing them on a whim. Gustavson et al. suggest that both procrastination and impulsivity involve a failure in goal management and a deficit in the ability to guide behavior effectively using goals. The authors refer to a hypothesis proposed by procrastination researcher Piers Steel that suggests impulsivity may have been adaptive to our ancient ancestors when survival depended more on thinking and acting quickly. In today's much safer world, however, planning for events yet to come has superceded impulsivity in terms of importance.

Thus, like many of our other bad habits, procrastination may have its roots in a behavior that was at one point adaptive and is now outdated. So, if it feels like your desire to procrastinate is driven by a force much stronger than your willpower, it may be so. If Gustavson et al. are correct, the impetus for procrastination lies in genetic programming that dates back to the Pleistocene era.

Gustavson, D., Miyake, A., Hewitt, J., & Friedman, N. (2014). Genetic Relations Among Procrastination, Impulsivity, and Goal-Management Ability: Implications for the Evolutionary Origin of Procrastination Psychological Science DOI: 10.1177/0956797614526260