One minute your teenage daughter is having a relaxed, happy conversation with her friend on the phone.
The next, she stumbles over an algebra problem and is -- instantly -- as angry as you've seen her. She flings her pencil across the room, stomps up to her room, slams the door and shouts, "I hate my life!"
Your teenage son appears to be in a good mood, and you ask him in your best modulated tone if he remembered to empty the dishwasher. "Why are you always yelling at me? I hate this family!" he shouts, storming out of the room.
For decades, parents have attributed such hair-trigger emotions to raging hormones, and they weren't wrong. However, in recent years more has become known about how brain development -- in concert with racing hormones -- accounts for how teens act and think.
Psychologist David Walsh has written a book, Why Do They Act That Way? (Free Press, $23), that offers an up-to-date explanation.
Walsh, president of the National Institute on Media and the Family in Minneapolis, says parents often think kids are deliberately misinterpreting situations or trying to drive their parents crazy, but this isn't the case.
It's because a teenager's prefrontal cortex -- the brain's center for moderation, impulse control and the understanding of consequences -- is still under construction. And the body's hormones -- which Walsh calls the accelerator center of the brain -- are surging.
In addition, he said, the adolescent brain processes visual stimuli or body language differently than grown-ups do. In a study that asked adults and teens to interpret facial expressions, adults were more likely to correctly identify emotions, while adolescents often mistook fear or surprise for anger.
"Adults use the rational part of the brain to read emotions," Walsh writes, "but adolescents basically do it with a gut reaction. And they are frequently wrong."
So, knowing all this, how can you better communicate with your child?
First, Walsh says, although it may not be the teen's "fault" that he is volatile or erratic or impulsive, that does not absolve him or her of responsibility. Teens must learn to control their behavior, "and it's your responsibility as a parent to help," Walsh writes.
He suggests sitting down with your teen in quiet times and discussing what behavior is expected and what the consequences will be if rules are not followed.
"Don't communicate the consequences as threats," he writes. "Just let him know in a matter-of-fact way what will happen and that the consequences will be his own choices."
The Hartford Courant is a Tribune Publishing newspaper.