The effects of simultaneous physical and cognitive task loads on physiological responses and component processes of decision making

Complex, dynamic decision making is prevalent in many domains in which there are also physically demanding tasks (e.g., military, athletics, and first responders). The state of the environment in this type of domain is constantly changing while critical decisions must be made. Decision making in this type of domain can be challenging, and this challenge is compounded by simultaneous physical exertion demands. Despite the occurrence of dynamic decision making during physical exertion in the real world, there is still little understanding of the effects of simultaneous cognitive and physical task loads on physiological responses and decision making. This is particularly true for the combination of complex cognitive tasks that require dynamic decisions making and physical tasks that require dynamic, whole body physical exertion. The objective of this dissertation was to investigate the effects of simultaneous physical and cognitive task demands on physiological responses and the component processes of decision making, as well as to determine if these effects change over time.;A laboratory experiment was conducted in which 40 participants walked on a treadmill at light to moderate exertion intensity while playing a complex, dynamic computer game (a microworld simulation). Both subjective and objective measures related to physical exertion and decision making were collected throughout the tasks.;Results demonstrated no change to physiological responses due to different cognitive task demands and no change to performance of the cognitive task due to different physical task demands. There were differential effects on situation awareness depending on the combination of task demands. Overall, moderate task demands (high physical task demands with low cognitive task demands or low physical task demands with high cognitive task demands) improved situation awareness, but higher task demands (high physical and high cognitive task demands) degraded situation awareness. Planning, prioritization and hypothesis generation were not affected by different cognitive and physical task demands. Subjective ratings of exertion, fatigue and workload demonstrated a U-shaped trend such that very low workload and very high workload received the greatest subjective ratings, with moderate workload condition ratings falling somewhere in between.;There was limited evidence that participants experienced whole body fatigue or that time on task affected cognitive or physiological measures of task performance. Participants' subjective experience did decline across sessions, perhaps due to lower body muscular fatigue.;These results have useful implications for real-world task design. This study suggests that tasks of light to moderate dynamic physical exertion can be performed for short periods of time without cognitive task performance decrements, with potential extension to a full 8-hour workday. However, care should be taken in task design since there is the potential for performance decrements in situation awareness and planning for longer task times. Future research is needed to investigate these effects for greater physical exertion intensities, longer time on task, and for comparison of simultaneous cognitive and physical task performance to performance of each task alone.