June 10, 2005 -- Like the proverbial deer caught in the headlights, people also freeze in response to fear.
A new study shows that the heart rate of men slows and movement ceases when they perceive a threat; merely viewing a disturbing image may be enough to induce this fear response.
Researchers say freezing or standing still when a threat is detected is a natural defensive reaction. This automatic behavior allows the prey to remain unnoticed by a potential predator.
Frozen by Fear?
In the study, which appears in the current issue of Psychophysiology, researchers examined the responses of 48 men to images selected to provoke unpleasant, neutral, or pleasant responses.
The men stood barefoot on a platform designed to measure body sway and balance and wore a heart monitor while they viewed 24 different pictures from the three categories. Unpleasant images depicted injured or mutilated humans, neutral ones showed objects, and pleasant images had sports scenes.
The results showed that when men viewed the images of mutilated humans, their body sway was significantly reduced and heart rate declined.
Researchers also found an increase in muscle stiffness after the participants viewed the unpleasant images.
They say this pattern resembles the 'freezing' seen in many animal species when confronted with threatening stimuli, which is controlled by nerve responses designed to promote defensive survival.