The Bomb in the Brain. Part 4

Transcription

1 The Bomb in the Brain Part 4

2 Fear Versus Reason The evolutionary primacy of the brain's fear circuitry makes it more powerful than reasoning circuits. The amygdala sprouts a profusion of connections to higher brain regions neurons that carry one-way traffic from amygdala to neocortex. Few connections run from the cortex to the amygdala, however. That allows the amygdala to override the products of the logical, thoughtful cortex, but not vice versa.

3 Fear and Evolution That makes fear "far, far more powerful than reason," says neurobiologist Michael Fanselowof the University of California, Los Angeles. "It evolved as a mechanism to protect us from lifethreatening situations, and from an evolutionary standpoint there's nothing more important than that."

4 Snakes on a Brain! Fear is not only more powerful than reason, however. It is also (sometimes absurdly) easy to evoke for reasons that also lie deep in our evolutionary past. Reacting to a nonexistent threat, such as fleeing from what you thought was a venomous snake that turned out to be a harmless one, isn't as dangerous as failing to react to actual threats. The brain is therefore wired to flinch first and ask questions later.

5 Experiment In a classic experiment, scientists compared people's responses to offers of flight insurance that would cover "death by any cause" or "death by terrorism. The latter, of course, is but a small subset of the former. Yet the specificity of the word "terrorism," combined with the stark images the word evokes, triggers the amygdala'sfear response in a way that "by any cause" does not. Result: people are willing to spend more for terrorism insurance than deathby-any-cause insurance.

6 Death and Ideology In one experiment volunteers who identified themselves as political conservatives were given reminders of mortality. After that prompt, they rated gay marriage, abortion and "sexual immorality" as greater threats to the nation than they had before the reminders. "When you remind people of their mortality, they defend their world view more strongly and reject those who challenge it," says Greenberg.

7 Biology and Ideology Now research suggests that such different reactions -and perhaps all political beliefs - might have a basis in biology. Oxley and Nebraska colleagues Kevin Smith and John Hibbing quizzed people on their political views, on topics ranging from the war in Iraq to capital punishment and premarital sex. All the participants had strongly held beliefs that identified them as socially liberal or socially conservative.

8 Revulsion and Ideology Two months after the survey, the researchers showed the subjects random pictures, while measuring how imperceptible changes in their perspiration affected skin conductivity. When an image of a bloodied face or maggot-filled wound appeared, conservatives sweated more than liberals, even after accounting for differences that might be due to sex, income, age or education. The same trend held for blinking in response to a loud, random noise. Conservatives blinked a little bit harder than liberals, an innate response to a threat, Hibbing says.

9 The Genetics or Environment? Oxley and Hibbing suspect that some genetic differences underlie our political leanings. Previous research has shown that certain mutations affect how a region of the brain called the amygdala reacts to fearful images.

10 The Liberal Brain Brains of liberals and conservatives may be constructed and work differently. Scientists at New York University and the University of California, Los Angeles, found that a specific region of the brain s cortex is more sensitive in people who consider themselves liberals than in self-declared conservatives.

11 Switching Gears The brain region in question helps people shift gears when their usual response would be inappropriate, supporting the notion that liberals are more flexible in their thinking.

12 The Conservative Brain A review of that research published in 2003 found that conservatives tend to be more rigid and closed-minded, less tolerant of ambiguity and less open to new experiences. Some of the traits associated with conservatives in that review were decidedly unflattering, including fear, aggression and tolerance of inequality.

13 The Experiment Participants were college students whose politics ranged from very liberal to very conservative. Scientists instructed them to tap a keyboard when an M appeared on a computer monitor and to refrain from tapping when they saw a W. M appeared 4 times more frequently than W, conditioning participants to press a key in knee-jerk fashion whenever they saw a letter.

14 W vsm Each participant was wired to an electroencephalograph that recorded activity in their anterior cingulatecortex, the part of the brain that detects conflicts between a habitual tendency (pressing a key) and a more appropriate response (not pressing the key). Liberals had more brain activity and made fewer mistakes than conservatives when they saw a W, researchers said. Liberals and conservatives were equally accurate in recognizing M.

15 The Numbers Liberals were 4.9times more likely than conservatives to show activity in the brain circuits that deal with conflicts and were 2.2 times more likely to score in the top half of the distribution for accuracy.

16 The This Is Your Brain on Politics

17 Maturity Versus Rigidity Overall, liberals show higher tolerance for ambiguity and complexity on psychological tests, and that conservatives tend towards needing greater structure and order.

18 Fear = Conservative When people fear death or terrorism, or are in a state of uncertainty, they tend to become more conservative A study of World Trade Center survivors after 9/11 reported that 38 percent grew more conservative in the 18 months following the attacks, as compared with only 13 percent who became more liberal.

19 Politics Is Bias Democrats and Republicans alike are adept at making decisions without letting the facts get in the way, a 2006 study shows. And they get quite a rush from ignoring information that's contrary to their point of view. Researchers asked staunch party members from both sides to evaluate information that threatened their preferred candidate prior to the 2004 Presidential election. The subjects' brains were monitored while they pondered.

20 Still Bias "We did not see any increased activation of the parts of the brain normally engaged during reasoning," said Drew Westen, director of clinical psychology at Emory University. "What we saw instead was a network of emotion circuits lighting up, including circuits hypothesized to be involved in regulating emotion, and circuits known to be involved in resolving conflicts."

21 A Lack of Reasoning The test subjects on both sides of the political aisle reached totally biased conclusions by ignoring information that could not rationally be discounted, Westen and his colleagues say. Then, with their minds made up, brain activity ceased in the areas that deal with negative emotions such as disgust. But activity spiked in the circuits involved in reward, a response similar to what addicts experience when they get a fix, Westen explained. The study points to a total lack of reason in political decision-making.

22 Politics IsIrrationality "None of the circuits involved in conscious reasoning were particularly engaged," Westensaid. "Essentially, it appears as if partisans twirl the cognitive kaleidoscope until they get the conclusions they want, and then they get massively reinforced for it, with the elimination of negative emotional states and activation of positive ones. Notably absent were any increases in activation of the dorsolateral prefrontal cortex, the part of the brain most associated with reasoning.

23 Part 4 next. References at