The Value of Looking Frightened
In The Expression of the Emotions in Man and Animals, Darwin suggested that the facial expression of being frightened was more than an expression—it functioned to help the frightened person cope with the threat. Finally there is evidence to support this idea. Researchers at the University of Toronto had volunteers mimic a frightened face and a "disgust" face. While posing the fear face subjects raised their brows, opened their eyes wider, and increased their horizontal eye movements; as a result, they increased their ability to detect peripheral objects. They increased their air intake and their nasal cavity, preparing them for physical exertion and, possibly, for taking in odors as well. When they mimicked disgust, they narrowed their eyes and scrunched up their nose and lips and decreased air intake. The authors propose that a frightened expression enhances perception and disgust dampens it. Nature Neuroscience, Vol 11, 843-850.
The Smell of Fear
"You could smell the fear in the air" is the stuff of mystery novels, but is there any basis in reality? As a matter of fact, the smell of fear is well documented in animals, and now we have a clue to how this fear signal is detected. Grueneberg ganglion cells were noticed in the nose of mice in 1973 and have been found in all mammals checked so far, including humans, but their function was unknown. Swiss researchers surgically destroyed these cells in mice and observed their behavior in the presence of pheromones collected from dying mice. Normal mice showed freezing behavior, crouching in a corner of the cage, while mice without the ganglion cells were obvlivious to the danger signal. Science, Vol 321, 1092-1095. You can read a brief description of the research and see a video here.
More on the Adolescent Brain
In Chapter 3 you learned that surging hormones aren't the only reason for conflicts between adolescents and their parents; the slower maturation of the prefrontal cortex also contributes to impulsive behavior. Now we have learned that during that time the amygdala puts on a burst of growth. In videotaped discussions of 137 early adolescents with their parents on topics that included bedtime, homework, and cell phone use, the ones who showed the most verbal aggression and aggressive facial expressions and tone of voice also had the largest amygdalas. Interestingly, boys whose left prefrontal cortex was larger than the right were less aggressive. Proceedings of the National Academy of Sciences, Vol 105, 3652-3657.
A Biological Basis for Political Attitudes?
Have you ever wondered why people hold such strong political and social views? Your first thought might be that they learn their attitudes during upbringing, but family and twin studies indicate a strong genetic influence*. Douglas Oxley and colleagues at the University of Nebraska asked whether political and social attitudes are related to individuals' sensitivity to threat. They located 46 people with strong political opinions, then measured their skin conductance response (which indicates autonomic arousal) to threatening images such as the sight of a bloody face, and their eye blink response to startling loud sounds. Those who were most responsive were more likely to take socially "protective" positions, supporting military spending, warrantless searches, the death penalty, the Patriot Act, obedience, patriotism, the Iraq war, and school prayer. The less responsive individuals had more favorable attitudes toward gun control, foreign aid, immigration, gay marriage, premarital sex, and abortion rights. On the basis of other research, the investigators suggest that the differences might be related to genetically based responsiveness of the amygdala. Science, Vol 321, 1667-1670. *See, for example, American Political Science Review, Vol 99, 153-167.
Sad News for the Old Folks
We knew that the elderly may experience some of the same problems as people with damage to the prefrontal cortex, such as performing poorly on tasks that require shifting strategies. Now we've learned that their prefrontal area is also less responsive to rewards. When younger people "won" in a simulated slot machine game, PET scanning showed increased dopamine production resulted in increased activity in the prefrontal cortex; in the elderly volunteers prefrontal ativity actually went down. This makes it easier to understand why some older people get less satisfaction out of life and have trouble making good decisions based on anticipated outcomes. Proceedings of the National Academy of Sciences, Vol 105, 15101-15111.
Moral Judgements and the Prefrontal Cortex
Although people with bilateral damage to the prefrontal cortex have difficulty applying moral and social rules in real life, they have no trouble doing so in laboratory exercises. However, recent research indicates one way they differ even in the lab; faced with a moral conflict, they are much more likely than normals to take a "practical" or "utilitarian" approach, opting for instance, to voluntarily sacrifice the life of one individual to save a number of others. The researchers interpret the result to indicate a blunting of social emotion. Nature, Vol 446, 908-911.
