Abstract: This document provides systems and methods for testing and assessing cognitive performance of a user over a period of time in order to test environmental effects and other factors on the performance of the user. For example, cognitive performance over a period of time can be assessed for users experiencing stress conditions including hypoxia (oxygen deprivation), hypothermia, sleep deprivation, fatigue or other factors that may cause degradation in cognitive performance. Furthermore, the systems and methods described herein can be used to identify when hypoxia has manifested in the cerebral circulation of an individual rather than merely in the extremities of an individual.