|M.Sc Student||Sahar Yotam|
|Subject||Grip Force as a Measure of Stress in Tracking Tasks|
|Department||Department of Industrial Engineering and Management||Supervisors||Professor Ido Erev|
|Dr. Michael Wagner|
|Full Thesis text|
High psychological stress is known to have adverse effects on task performance and it is therefore of great importance to know when individuals are under stress. In the current research we tested the validity of Grip Force as a measure for psychological stress. Commonly used stress monitoring and measurement tools suffer from substantial delays, in such a manner that makes it difficult to use these aids in real-time environments. Grip Force is equivalent to muscle tonus, which is known to be affected by stress with almost no delay. Previous research on Grip Force found that Grip Force reacted to workload but none actually manipulated stress. In this research stress was induced during the performance of a psychomotor task, in order to investigate whether Grip Force is affected by stress. In addition, Grip Force was compared to commonly used stress measures. Thirteen participants performed joystick controlled tracking tasks in exchange for course bonus points. The experimental group's bonus points were linked with their performance of the task, in order to manipulate stress. The control group's bonus points were constant. An LMM analysis revealed a significant interaction effect on Grip Force between experimental half and group, F(1,425)=25.016, p<0.001. Grip Force increased in the last two sessions of the experiment (2nd half) only in the experimental group, where participants could lose part of their bonus points. In the control group Grip Force diminished between the 1st and 2nd halves of the experimental procedure from mean of 0.334 (SE= 0.115) to mean of -0.354 (SE= 0.119). In the experimental group Grip Force increased from mean of -0.148 (SE= 0.077) to mean of 0.006 (SE= 0.120). Furthermore, Grip Force complied with commonly used stress measures - self-reported stress and skin conductivity. Self-reported stress showed a pattern of results similar to those of Grip Force. An LMM analysis revealed a significant interaction effect on self-reported stress between experimental half and group, F(1,425)=6.287, p<0.05. In the control group subjective stress ratings diminished from mean of 0.124 (SE= 0.114) to mean of -0.143 (SE= 0.117). In the experimental group subjective stress ratings increased from mean of -0.114 (SE= 0.076) to mean of 0.152 (SE= 0.118). In addition there was a significant correlation between GSR and FSR (r=0.45, p<0.001). These findings confirm the main hypothesis and lend support to the use of Grip Force as a measure of stress in psychomotor tasks.