MONDAY, June 20, 2005 (HealthDay News) -- Like a deer in the headlights of a car, humans tend to freeze when they encounter a threat, and this reaction may harken back to a time when standing still meant going unnoticed by a predator, Brazilian researchers conclude.
Reporting in the journal Psychophysiology, investigators at the Federal University of Rio de Janeiro studied 48 male volunteers. They found that even showing the men a photo of an injured person or a mutilated human body could cause them to suddenly stand still.
Furthermore, as they viewed these unpleasant images, the men's heart rates dropped, their muscles stiffened and there was a significant reduction in their body sway.
"This pattern resembles the 'freezing' and 'fear bradycardia' [slowed heartbeat] seen in many species when confronted with threatening stimuli," study author Eliane Volchan said in a prepared statement. She said this response is "mediated by neural circuits that promote defensive survival."
This freezing is considered by experts to be a protective reaction that increases the odds that a prey animal will go unnoticed by a predator.
The Nemours Foundation has information about fears and phobias.