Towards creating air force pilots' selection model: A comparison between most accurate mental stress markers in contact and non-contact techniques

Recently in modern wars, spying and military activities, especially military aviation, are turning to be computer related war with a significantly low physical activities that are based mainly on mental workload. Furthermore, long exposure to sever mental stress levels leads to mental illness and the military personnel start to lose moral spirit, focus, and start gradually to lose the ability of doing the mission in a correct manner. Consequently, a model should be designed and implemented to classify the subjects according to the mental stress level they can tolerate. A modified version of Stroop color stressor is used in three different levels of difficulty, each level varies in the duration of the trial time available to respond. Mean heart rate and mean pupil diameter were acquired for different mental stress levels in addition to the resting phase. These derived markers were compared to each other for all mental stress levels in order to get a relationship that can describe the mental stress state. Finally, the two markers show different responses for the mental stress applied to subjects. Mean heart rate did not reveal a general behavior for various mental stress levels for all subjects. However, mean pupil diameter was a successful marker in solving this issue, and it was proved to reveal a common increasing response to the increased mental stress level for all subjects.