structural:reformatting, structural:summarization
Effects of stress

Both surprise and stress induce physiological response: elevate heart rate substantially. In a study conducted on 8 female and male student actors ages 18 to 25, their reaction to an unforeseen occurrence (the cause of stress) during a performance was observed in terms of heart rate. In the data collected, there was a noticeable trend between the location of actors (onstage and offstage) and their elevation in heart rate in response to stress; the actors present offstage reacted to the stressor immediately, demonstrated by their immediate elevation in heart rate the minute the unexpected event occurred, but the actors present onstage at the time of the stressor reacted in the following 5 minute period (demonstrated by their increasingly elevated heart rate). This trend regarding stress and heart rate is supported by previous studies; negative emotion /stimulus has a prolonged effect on heart rate in individuals who are directly impacted. In regard to the characters present onstage, a reduced startle response has been associated with a passive defense, and the diminished initial heart rate response has been predicted to have a greater tendency to dissociation. Current evidence suggests that heart rate variability can be used as an accurate measure of psychological stress and may be used for an objective measurement of psychological stress.