Analyzing Individuals' Grip Force over Short Intervals in a Joystick-Controlled Task with and without a Stress Manipulation

The current experiment is part of an ongoing feasibility testing of grip force as a measure of stress in joystick-controlled tasks. In a previous experiment, we showed that mean grip force of a group of students was higher under a stress manipulation, and higher than of another group of students with no stress manipulation. In the current experiment, we tested if we could identify greater grip force under stress, per individual. Fourteen male participants performed tracking tasks on trials with and without a stress manipulation. After the experiment, we computed the mean grip force of each participant in several intervals to test how soon (if at all) his mean grip force on the trials with the stress manipulation had become significantly higher than his mean grip force on the trials without the stress manipulation. In ∼31% of the comparisons we were able to detect higher grip force with than without the stress manipulation after 5 seconds through the trials. Other detections of greater grip force took longer, but no longer than 30 sec. However, we could not find significant changes in grip force in certain comparisons for six individuals, and in none of the comparisons for four individuals. The sources and extent of these limitations of grip force as a measure of stress should be explored in future studies. The current experiment added support to the feasibility of using grip force as a measure of stress in joystick-controlled tasks and pointed to the next necessary steps in evaluating its feasibility.