Third, the human operator when exposed to a workload can meet the requirements of the same problem by the voltage of the various components of their behavior, or support functions. For example, with increasing performance requirements of the task is often maintained without any violation of it, whilst subjective evaluation or functional characteristics indicate an increase in force or activation. Occupational stress is largely determined by operational requirements, which are related to the nature of the workload. This relationship is seen in two types of models. Model matching personality and environmental conditions designed J. R. P. French et al. , R. V. Harrison  and others, it shows that the operating voltage is caused by a mismatch between job requirements and human capabilities of its individual resources. Stress can result from any excessive demands and unmet needs.