Christina Aguilera Flub: What Was Inside Her Mind?

(CBS) Football fans expect fumbles - just not the sort Christina Aguilera committed while singing the "Star-Spangled Banner" before last night's Super Bowl.

The sexy songstress left out the part about the "ramparts," later explaining that she got so caught up in the moment that she lost her place.

How could that happen? After all, Aguilera, 30, says she has been singing the National Anthem since she was seven, Us magazine reported.

One possible explanation: performance anxiety, a.k.a. stage fright. It's a common problem among singers and other performing artists.

"It's not unusual," Dr. Julie Nagel, a psychologist in private practice in Ann Arbor, Mich., tells CBS News. "It's like having an accident on slippery ice. People think that if they prepare enough it can't happen. But deep down they know it can."

Stage fright can have various causes, including difficult early childhood experiences, says Dr. Nagel, who has no first-hand knowledge about what caused Aguilera's difficulties last night. But whatever the cause, there are effective ways to treat it.

Psychotherapy is one option, Dr. Nagel says. Medications can help too. The prescription drug propanolol (Inderal), for example, can help performers control shaking and other physical signs of anxiety - though not the anxious thoughts that can exacerbate the problem.

And Dr. Nagel, a Juillard-trained pianist whose own stage fright led to a career change, says it's critical that performers who experience stage fright talk about their problem. "It is not something that is forbidden," she says. "It's something that is a real issue that needs to be talked about."