Cognitive methods for assessing mental energy.

Mental energy is not well defined but of considerable public interest. Although the physical energy required to complete a task can be objectively specified, the concept of mental energy is relatively new. Mental energy is a mood, but can also be defined as ability or willingness to engage in cognitive work. This review addresses the concept of mental energy and cognitive tests used to assess it. Methods that can be used to assess mental energy, including tests of cognitive performance, mood questionnaires, electrophysiological techniques, brain scanning technologies, and ambulatory monitoring, are discussed. Studies of the factors affecting mental energy, such as drugs, foods, sleep deprivation, and disease states, are also reviewed. In aggregate, the studies reviewed suggest use of cognitive tests that assess vigilance, ability to sustain attention, and choice reaction time are optimal for assessment of mental energy. Specific tests recommended include the psychomotor vigilance task, Wilkinson four-choice visual reaction time, the scanning visual vigilance test, and Wilkinson auditory vigilance test. These tests are sensitive to factors that both increase and decrease mental energy. Critical factors in the design and conduct of studies used to assess mental energy are also discussed.