No. Most symbols need to be learned. They are best used to reinforce the warning text. Moreover, recent test measuring the psychophysiological responses of men versus women show that symbols are not always best. Men respond proportionately higher to a symbol, yet women respond more to text.

These studies completed at the University of Florida measure brain waves, EKG, the startle response, muscle tension and blood pressure when the test subjects viewed various warning signs and symbols. The illustration here shows how psychophysiological tests measure a subject's "startle" response to the viewing of a symbol and, simultaneously being surprised with a loud noise or bright light.

Reprinted from Psychological Review 97, 377-395, with permission of Dr. Lang and the American Psychological Association

This illustration shows one psychophysiological test. Electrodes are placed onto various facial muscles. The subject is shown a series of good and bad symbols and safety signs. During the period that the subject is looking at a particular sign, a loud noise or bright light suddenly occurs ("the startle"). The subject has an automatic "startle" reflex that is innate. The magnitude of this startle reflex helps measure the power of the warning message or symbol. This is a common technique in brain research and is now being used to evaluate many of our symbols and safety signs.