Objective: We conducted an exploratory investigation of whether grip force could be an indicator of stress in aviation. Background: Pilots might experience stress when anticipating failure to meet task demands and therefore, higher levels of stress can be used as a trigger for engaging automatic assistance. An unobtrusive measure of stress in aviation might be the grip force pilots exert on the control stick that could increase due to the intensified muscle tonus that characterizes psychological stress. Method: Participants were randomly assigned to either an experimental or a control group and performed tracking tasks. Participants in the experimental group were told that as of the second half of the experiment their compensation for the experiment would partly depend on their performance. No such conditioning existed for the control group. Grip force was then measured using a sensor on the control stick. Results: Grip force significantly increased in the second half of the experiment in the experimental group, but decreased in the control group. Similar interaction between experimental group and experimental half was also evident with self-reported stress and galvanic skin response (GSR), yet increases within the experimental group were not significant. Grip force also moderately correlated with GSR, possibly suggesting that they responded to the same construct. Conclusion: Findings provided a preliminary indication that grip force could be used to measure stress in aviation, meriting further research exploration.

Objective: To study the relationship between physiological indices and kinematic indices during braking events of different intensities. Background: Based on mental workload theory, driving and other task demands may generate changes in physiological indices, such as the driver’s heart rate and skin conductance. However, no attempts were made to associate changes in physiological indices with changes in vehicle kinematics that result from the driver attempts to meet task demands. Method: Twenty-five drivers participated in a field experiment. We manipulated braking demands using roadside signs to communicate the speed (km/h) before braking (50 or 60) and the target speed for braking (30 or to a complete stop). In an additional session, we asked drivers to brake as if they were responding to an impending collision. We analyzed the relationship between the intensities of braking events as measured by deceleration values (g) and changes in heart rate, heart rate variability, and skin conductance. Results: All physiological indices were associated with deceleration intensity. Especially salient were the differences in physiological indices between the intensive (|g| > 0.5) and nonintensive braking events. The strongest relationship was between braking intensity and skin conductance. Conclusions: Skin conductance, heart rate, and heart rate variability can mirror the mental workload elicited by varying braking intensities. Application: Associating vehicle kinematics with physiological indices related to short-term driving events may help improve the performance of driver assistance systems.