title: Mental workload in heat: toward a framework for analyses of stress states.
abstract: BACKGROUND
  Effects of stress on performance are often interpreted by recourse to the arousal theory, which accounts for performance effects only in relation to the level of nervous system activity. This omits voluntary control that may be exerted in moderating stress effects. The present work elaborates on two control processes (viz., strategies and effort exertion) from the standpoint of the theory of mental workload, which was assessed in two experiments as a function of task demand and heat stress. Task demand was varied by increasing the complexity of decision rules and by presenting feedback indicating efficiency of task-strategies.
  
  
  OBJECTIVE
  As decision rules are made more complex, task demand increases, causing longer reaction time (RT) and higher workload. Feedback improves performance by affecting strategies and effort exertion. Heat's effect on performance is related to the generated thermophysiological state and degree of effort exerted to maintain efficiency.
  
  
  METHODS
  Performance and workload were measured in a decision-making task as a function of complexity of decision rules and feedback in 22 degrees C and 40 degrees C temperature conditions. Workload was measured by secondary task RT (STRT), subjective rating of effort (SRE), and heart rate (HR). Core temperature (Tc) was monitored continuously.
  
  
  RESULTS
  Primary task RT (PTRT), STRT, SRE, and HR increased as complexity of decision rules increased. Feedback decreased PTRT, and increased STRT, SRE, and HR. In heat, a higher Tc was associated with a shorter PTRT and a longer STRT.
  
  
  CONCLUSIONS
  A substantial part of variation in adaptation to demand was accounted for by control processes that involved higher cognitive functions.
authors.affiliation: Swedish National Institute of Occupational Health.
authors.forename: S
authors.initials: S
authors.lastname: Razmjou
mesh_terms: D000328:Adult; D003657:Decision Making; D006358:Hot Temperature; D006801:Humans; D008297:Male; D008606:Mental Processes; D013315:Stress, Psychological; D013647:Task Performance and Analysis