Biting of nails or teeth

You bite your nails or grind your teeth.

Type A’s are more prone to nervous behaviors like nail biting, teeth grinding and fidgeting. This symptom of Type A behavior goes back to Friedman’s early research. While working with his patients who had heart disease, Friedman noticed that many of them had a habit of grinding their nails into a chair in his office (deep enough to leave marks), which he took to indicate a heightened state of agitation, Schaubroeck explains.