Mental chronometry is the scientific study of processing speed or reaction time on cognitive tasks to infer the content, duration, and temporal sequence of mental operations.
Mental chronometry uses measurements of the elapsed time between sensory stimulus onset and subsequent behavioral responses to study the time course of information processing in the nervous system. Distributional characteristics of response times, such as mean and variance, are considered useful indices of processing speed and efficiency, indicating how quickly an individual can perform task-relevant mental operations. Behavioral responses are typically keystrokes, but eye movements, vocal responses, and other observable behaviors are often used. Reaction time is thought to be limited by the speed of signal transmission in white matter as well as the processing efficiency of neocortical gray matter.
The use of mental chronometry in psychological research is wide-ranging, including nomothetic models of information processing in the human auditory and visual systems, as well as differential psychology topics such as the role of individual differences in RT in human cognitive ability, aging, and a variety of clinical and psychiatric outcomes. The experimental approach to mental chronometry includes topics such as the empirical study of vocal and manual latencies, visual and auditory attention, temporal judgment and integration, language and reading, movement time and motor response, perceptual and decision time, memory, and subjective time perception. Conclusions about information processing drawn from RT are often made with consideration of experimental task design, limitations of measurement technology, and mathematical modeling.