Embarrassment is what's known as a self-conscious emotion. While basic emotions such as anger, surprise or fear tend to happen automatically, without much cognitive processing, the self-conscious emotions, including shame, guilt and pride, are more complex. They require self-reflection and self-evaluation.

Typically, a set of behaviors unfolds over time when a person is embarrassed: A woman who calls a new acquaintance by the wrong name, for example, will likely gaze downward, suppress a smile, turn her head away and then shift her gaze. (Blushing is also common, but it's not universal, Harris says.) Behind the scenes, there's a distinct physiological pattern taking place. In emotions such as anger and fear, both heart rate and blood pressure spike. In embarrassment, Harris found, these two measures spike initially — but soon heart rate slows down again, while blood pressure continues to rise (Journal of Personality and Social Psychology, 2001). "That coupling might be a unique signature to embarrassment," she says.

Where does embarrassment arise in the brain? Recently, Virginia Sturm, PhD, an assistant professor of neurology at the University of California, San Francisco, and colleagues tracked down a bit of gray matter that appears to play a major role in embarrassment. Sturm studied patients with a form of frontotemporal dementia, a degenerative brain disease that causes profound changes in personality and behavior. Patients with the disease often say or do socially inappropriate things without seeming to feel any humiliation. She found that a brain region called the right pregenual anterior cingulate cortex was smaller in people who suffered from the disease.

That region seems to spawn embarrassment in healthy people, too. Sturm found that healthy control subjects who weren't easily embarrassed by watching videos of themselves singing the 1964 hit "My Girl" had a smaller pregenual anterior cingulate cortex than healthy controls who were more mortified by the performance.

Psychologists are quick to point out that there's a significant difference between shame and embarrassment. "A lot of people intuitively think there's a connection, that embarrassment is a weaker form of shame," says June Tangney, PhD, a psychologist at George Mason University. But that seems not to be the case.

Shame, she's found, is much more intense and likely to be associated with moral transgressions. And while most people feel shame in the company of others, "solitary" shame is not uncommon, she says. Embarrassment, on the other hand, tends to stem from social slip-ups, and we rarely experience it outside a social context. Embarrassed folks are also more inclined to laugh about an embarrassing incident. "When people feel shame," she says, "there's no sense of humor about it at all."

—Kirsten Weir