A world full of extroverts would be a terrible place. And unbearably loud.

Shy people, the introverts, are an essential counterweight on the balance scale of human behavior. But there’s a difference between shyness and social phobia, one of five major types of anxiety disorders, punctuated by an all-consuming anxiety and extraordinary self-consciousness in common social situations.

“It’s always a bit arbitrary, but where we tend to draw the line is in the area of functioning,” said Dr. David Tolin, founder and director of the Anxiety Disorders Center at the Institute of Living, as part of  a panel discussion on shyness on WNPR’s “Colin McEnroe Show” earlier this week. “If the person is shy, yet the function OK, we would usually consider that to be within the broad range of normal.”

Dr. Tolin, author of “Face Your Fears: A Proven Plan to Beat Anxiety, Panic, Phobias, and Obsessions” (John Wiley & Sons), says the benchmark is when that function disrupts a shy person’s life.

“It’s only when you start seeing that the person is just miserable,” he said, “that they can’t social socialize in the way that they would like or they can’t work in the way that they would like or they can’t concentrate because they are so socially preoccupied and things are starting to go bad for them because of it. That’s usually where we would say, ‘You’ve got something that needs to be addressed.'”

Dr. Tolin was joined on the panel by Joe Moran, professor of English and cultural history at Liverpool (England) John Moores University and author of “Shrinking Violets: The Secret Life of Shyness,” and Susan Cain, author of “Quiet: The Power of Introverts in a World That Can’t Stop Talking and the founder of Quiet Revolution.” In a possible surprise to listeners, chat-master McEnroe also described himself as a shy person who flounders in certain social situations.

Though most people agonize over a specific action, such as public speaking or a socializing at a party — “I’m shy at parties,” said Dr. Tolin, “so I’ll just hang out at the buffet and not really engage with people as much” — 12.1 percent of American adults experience  in their lifetime a more serious problem, social phobia, that interferes with work or school and even makes it difficult to form relationships.

Symptoms of social anxiety, according to the National Institute of Mental Health, include:

  • Anxiety about being with people.
  • Difficulty talking to people.
  • Self-conscious in front of others.
  • Worried about feeling humiliated or embarrassed.
  • Afraid others will judge you.
  • Worrying for days or weeks before an event.
  • Avoiding places where people gather.
  • Difficulty making, keeping friends.
  • Blushing, sweating or trembling when around other people.
  • Feeling nauseous when around other people.

Social phobias and other anxiety disorder are usually treated with therapy or medication, or both. Dr. Tolin, whose latest book is “Doing CBT: A Comprehensive Guide to Working with Behaviors, Thoughts, and Emotions” (The Guilford Press),  said he tries to get his patients to confront the situations that induce anxiety.

“So if the person is becoming terribly avoidant of talking to new people or meeting them,” he said, “then it would not be at all uncommon for me to walk that person up and down the halls of the Anxiety Disorders Center at the Institute of Living and introduce them to all the people there and have them practice shaking hands and making small talk. It’s uncomfortable at first, but after a while they get used to it and it’s not so bad.”

Next, he said, he’ll try to dig beneath the surface to find out why patients behave in a certain way and then get them to challenge it.

“Sometimes,” he said, “the person does have a very poor sense of self, but not always. Sometimes they just have this really debilitating fear that something they do is going to look stupid or embarrassing and it’s just going to be terribly humiliating. All of those are things we have to address when we’re treating somebody who’s at at the extreme end of the shyness continuum.”