Human motor control, autonomic and decision processes under physical and psychological stress. Instinctive, reflexive and adaptive aspects.

The stress response is governed by automatic neurological and hormonal processes that occur before we become consciously aware of a dangerous situation. If stress ensues for 15-30 seconds, the hormonal processes may have progressed so far that recovery takes an hour or longer instead of minutes. Stress can affect our behavior and in certain professions, such as the police force and emergency services, being in stressful situations is routine. When the stress imparted on an action is low, there may be little detriment to performance. However, when the stress imparted on an action is high, performance may be reduced and viewed as unsatisfactory.
This thesis has examined the situational characteristics and performance of police officers in stressful incidents where firearms and pepper spray have been used, and during training scenarios designed to induce stress. Pepper spray and firearms were often used differently in real situations, both operationally and technically, compared to the way they were used during training. When armed assailants were encountered in actual incidents, weapons were often used late on and at very short ranges. One real life event studied in detail showed that both police officers and civilian witnesses suffer from similar perceptual and memory distortions. When mimicking real situations for training through simulations, stress levels increased as evidenced by an increase in heart rate which may be used to ensure the closeness of training simulations to real events. When assessing the suitability of pupil dilation as a stress measure, the pupil underwent dilation in spite of large illumination increases, and the pupils also dilated when a threat emerged early in stress-inducing scenarios. Subjective assessments made by six experts separately, rated performance as being impaired in the simulated stress training in addition to poorer performance of a highly trained, complex, motor skill.
To conclude, stress can affect police officers during interventions and training, as it impaired perception and memory, cognition, decision-making and the motor skills necessary for equipment and weapon use. Hence, the consequences of stress responses should be considered when designing tactics, training and equipment so that tasks can be carried out well when stress is heightened. An increased understanding of physiological and behavioral changes to stressful situations in police officers will contribute to rationalizing outcomes and influencing policy based on scientific empirical and physiological grounds.