Abstract: Vigilance concerns the basic human capacity for information processing and is therefore essential to any form of human cognition. Both physical and mental effort are thought to affect vigilance. Mental effort is known for its vigilance declining effects, but the effects of physical effort are less clear. This study investigated whether these two forms of effort affect the EEG (Electro-EncephaloGram; measure of brain activity) and subjective alertness differently. Participants performed a physical task and were subsequently presented with a mental task, or vice versa. Mental effort decreased subjective alertness and increased theta power (i.e. waves with low frequency) in the EEG. Both results suggest a vigilance decline. Physical effort, however, increased subjective alertness and alpha and beta1 power in the EEG. These findings point towards an increase in vigilance. Beta2 power was reduced after physical effort, which may reflect a decrease in active cognitive processing. No transfer effects were found between the effort conditions, suggesting that the effects of mental and physical effort are distinct. It is concluded that mental effort decreases vigilance, whereas physical effort increases vigilance without improving subsequent task performance.
Abstract: Research suggests opposing alertness effects of mental effort and physical effort: mental effort seems to decrease and physical effort appears to increase subjective alertness. There are indications, however, that physical exercise also leads to feelings of lowered alertness. The well-known multidimensional Thayer alertness scale does not seem to assess physical alertness properly. New items were added to the original scale; these were expected to form a physical factor of subjective alertness. In part 1 of this study, participants filled in the revised Thayer scale before and after a control condition and conditions of physical and mental exercise. Physical exercise only increased feelings of physical fatigue, not of alertness. Mental effort increased feelings of sleepiness. In part 2, a Factor analysis was performed on a larger data set in order to validate the use of a separate physical factor. Indeed, a separate physical factor was found. Besides this physical factor, the analysis revealed the factors “sleepiness”, “calmness”, and “tension”, which have originally been described by Thayer. In conclusion, physical alertness is different from mental alertness. Therefore, an explicit physical factor is required in subjective alertness scales.
Abstract: The term vigilance is used frequently in a wide variety of research areas. The British neurologist Sir Henry Head introduced the term to refer to a state of high consciousness. Nowadays, ‘vigilance’ is used in neurophysiological research, but also in the experimental psychological field. Related terms, such as arousal, sustained attention, and tonic alertness are often used jointly with or instead of the term vigilance. It may seem that all these designations can be interchanged freely, but this is not the case. Many investigators differentiate these terms and the distinctions made are not always subtle. The terminological confusion of vigilance involves on the one hand its definition (i.e. clarification of the theoretical construct) with reference to different processes, and on the other hand different measuring procedures. The original definition of vigilance: “… a high state of physiological efficiency” is rather physiological in nature, but the “efficiency” part points to behavior. Head’s clarification that a vigilant state differs from a pure condition of raised excitability appears to be of major importance. The combination of physiological activity and efficient behavior is of great relevance and underlines the difference between vigilance and more basic energetic conditions.
The topic of this paper is the exploration of procedures for measuring vigilance. EEG-measures are very popular and are described first. More specifically, the spectral content of the EEG is investigated. Second, behavioral measures are presented. These concern performance on vigilance tasks. Finally, subjective questionnaires are explored.