ARI SHAPIRO, HOST:
Can a fruit fly get angry? And if so, is it anything like the anger we hear from this guy?
(SOUNDBITE OF ARCHIVED RECORDING)
LEWIS BLACK: I was told my tax dollars were going to murdering monkeys in space. And now you're telling me they're just faking it in a Jacuzzi?
SHAPIRO: That is the comedian Lewis Black. As part of NPR's series on anger, Black and NPR's Jon Hamilton explore the biological roots of a powerful emotion with a bad reputation.
JON HAMILTON, BYLINE: For Black, anger is a job.
BLACK: The anger that I do onstage is - I'm acting.
HAMILTON: But his performances are fueled by real anger. And Black has spent decades thinking about how this emotion works in his own brain.
BLACK: My anger comes from a collection of things that occur during the course of a day that build up. So by the end of a day, 67 things have happened to me that have gone into my anger bank.
HAMILTON: What sort of things?
BLACK: Idiotic debates that go on in Congress, health care, your cable provider.
HAMILTON: Onstage, Black leans forward. He shouts. He gestures with an index finger.
(SOUNDBITE OF ARCHIVED RECORDING)
BLACK: Right now I'm on Snapchat. That's right - Snapchat. This is what I've sunk to.
HAMILTON: To a scientist, he looks a lot like a belligerent dog or an irate gerbil. David Anderson is a neurobiologist at Caltech who studies aggression in animals.
DAVID ANDERSON: Practically every sexually reproducing multicellular animal shows aggressive behavior. Fruit flies show aggression.
HAMILTON: Anderson is the co-author of a book on the neuroscience of emotion. He also studies fruit flies.
ANDERSON: They fight over females. They fight over food. They threaten each other. They put their wings up in the air. They charge at each other.
HAMILTON: So are these animals angry? Anderson says that depends how you define the term.
ANDERSON: We use anger to refer to our experience - our conscious experience of rage, the feeling that you are about to explode, the feeling of irritation.
HAMILTON: But feelings are hard to study in a fruit fly and other animals, so scientists like Anderson focus on their behavior or on biological changes like heart rate and hormone levels and brain activity. By these measures, aggression appears remarkably consistent across species. For example, Anderson says both animals and people may take out their aggression on innocent bystanders. His cat does this.
ANDERSON: It can be staring out the window, and a neighborhood cat strolls by. Its back arches. It hisses. Its tail goes up, and it turns around and attacks my other cat who's been sitting placidly by, minding her own business.
HAMILTON: Anderson says animals also can act angry long after the source of their irritation is gone. Both Anderson and Black say anger and aggression can be useful. Black says expressing anger during performances helps him maintain his internal balance.
BLACK: I have the best blood pressure of anybody I know, and I think it has to do with the fact that I've spent a lot of my life yelling and screaming about things onstage.
HAMILTON: He may be right. There is evidence that expressing anger can reduce levels of a stress hormone. On the other hand, extreme outbursts may trigger a heart attack. And of course, being on the receiving end of this emotion can hurt. But for Black, anger is a powerful motivator.
BLACK: What anger is good for, too, is to generate energy to move on to figure out how to do something. And that's really what it's good at in terms of the community. You get angry and go, what do we do?
HAMILTON: Anderson says in the animal world, an aggressive response can help a creature survive if it's attacked or robbed.
ANDERSON: If a squirrel steals a nut from another squirrel, there is an adaptive value to arousing the squirrel who is the victim of the theft and having it chase at the other squirrel and beat him up and try to recover has nut.
HAMILTON: Anderson says in both animals and people, aggressive behavior tends to be associated with physical responses like a racing pulse, higher blood pressure and elevated levels of hormones, including testosterone. And he says the similarities raise a question about brain evolution and aggression.
ANDERSON: You look at dogs fighting. You look at fish fighting. You look at flies fighting. They're all fighting with each other. You look at people fighting. Is that because they're all using the same basic brain mechanisms and brain chemicals?
HAMILTON: There is a working theory that because aggression is so common - because it's not just a reflexive response - the feeling behind it must be common, too. If so, that suggests the potential for anger is something we're born with. There's an ongoing debate among scientists about whether that's true, but Black thinks it is, and so does Marcel Just, a neuroscientist at Carnegie Mellon University in Pittsburgh.
MARCEL JUST: I'm sure there's a strong biological component.
HAMILTON: Just is one of a few scientists who have actually studied anger in human brains, and what he found was surprising.
JUST: Even though everybody's anger feels very personal - and how could my anger possibly resemble yours? But in fact, if we were both in an MRI scanner and measured the activation, the pattern would be rather similar.
HAMILTON: Just was part of a study that trained a computer to recognize the brain activity associated with anger in people, and it was able to identify the emotion most of the time. Just says one way the human brain may differ from an animal's is in the circuits used to control emotions, including anger. And he says our ability to use these circuits probably depends more on nurture than nature.
JUST: One of the things that we learn from our families, from our parents, from our teachers is how to deal with our various emotions and most particularly anger.
HAMILTON: Lewis Black says he's spent much of his life learning how to deal with his anger, and he understands why the emotion gets such a bad rap.
BLACK: It's where it leads to that it's gotten its rap. Disgust - you may lose a friend, you know? Anger - you could kill a friend.
HAMILTON: So Black says when he's out performing, he often finds himself trying to make sure an audience doesn't get too angry. And if he finds his flight home has been delayed, he stays calm.
BLACK: Here's a million-dollar tip. You sit on that anger, and you just empathize with the person whose job it is to deal with you.
HAMILTON: Jon Hamilton, NPR News.