Unemotional data on startle response.

Some psychologists believe that the startle reaction, which has been examined by numerous researchers since 1939, lies at the far end of the emotion of surprise and provides a good model for the study of other emotions. Others say it is a reflex and add that bona fide emotions occur after internal appraisals of thoughts or events.

Detailed measurements of facial muscles during the startle reaction suggest that it is probably a reflex, according to a report in the November JOURNAL OF PERSONALITY AND SOCIAL PSYCHOLOGY. Still, it is not yet clear whether prior appraisal is always necessary to arouse emotions, say psychologists Paul Ekman and Wallace V. Friesen of the University of California at San Francisco and Ronald C. Simons of Michigan State University in East Lansing.

The researchers examined the startle reactions of 17 healthy individuals who, on different occasions, did or did not know when a blank pistol would be fired. Subjects were also asked to suppress startle responses after being warned of an impending gunshot and to simulate a startle when there was no gunshot. High-speed motion pictures were used to analyze facial expressions.

Within 200 milliseconds after an unanticipated startle, most subjects displayed horizontal stretching of the lips, tightening of eye and neck muscles, eye blinking, eyebrow lowering and jerking of the head and trunk. Responses to anticipated startles were similar but less intense. Subjects had little success in squelching their responses to the gunshot and also had problems simulating a startle reaction.

With emotions such as surprise, happiness and disgust, note the researchers, facial expressions can be inhibited and simulated fairly successfully and are far more difficult to elicit experimentally than is the startle reaction.

Some psychologists who argue that prior appraisal is not required to experience emotion also contend that data on the startle reaction would resemble findings for other emotions if stimuli as strong as the blank pistol shot were used. But the startle is unique in two ways, say the investigators. While several recent studies indicate that the same muscle movements are made in moderate and extreme emotional expressions, different muscles are used in surprise and startle reactions; thus, the startle is not "extreme surprise." And even with strong stimuli, no single emotional expression has been shown by all subjects on the first trial; a gunshot, however, always produced a startle reaction in all subjects.