A method for measuring human behavioural and physiological responses at different stress levels in a driving...

1. A method is described by which a car simulator can be used to measure, simultaneously, motor-perceptual performance and physiological responses of human subjects under different levels of task difficulty or stress.2. Motor-perceptual performance was measured in terms of reaction times taken by subjects to carry out steering, braking and operation of traffic indicators in the simulator. Subjects were instructed to carry out the different driving manoeuvres by means of a command panel containing five coloured lights. Three levels of task difficulty or stress were devised. In level 1 only the light signals were used. In level 2 the driving simulator film was shown and all of the light signals reinforced the movements of the car in the film. Level 3 was similar to level 2, with the exception that whilst some of the light signals reinforced the movements of the car, others deliberately conflicted with it.3. Physiological responses measured were heart rate, blood pressure, respiration and calf blood flow. Personality was also measured by means of the Cattell 16 personality factor questionnaire.4. Analysis of variance of the performance of 15 subjects showed significant variation between the three task levels (P=<0.001 for steering reaction times; P=<0.01 for brake and indicator reaction times). In all cases the reaction times were longest for level 3, indicating that this was the most difficult task. The number of anticipated responses to steering, braking and traffic indicator signals was highest in level 2, while the number of corrections to steering and braking responses was lowest in level 2. None of these differences was statistically significant.5. Of the physiological variables, the heart rate showed a progressive increase from task levels 1 to 3 but only those between levels 1 and 3 were statistically significant (P<0.05).6. The results are discussed in relation to the validity of the method. It is concluded that by means of this method it is possible to produce controlled and reproducible degrees of stress and under conditions which are also suitable for the investigation of pharmacological agents upon it.