Mental chronometry

Mental chronometry uses measurements of elapsed time between sensory stimulus onsets and subsequent behavioral responses. It is considered an index of processing speed and efficiency indicating how fast an individual can execute task-relevant mental operations. Behavioral responses are typically button presses, but eye movements, vocal responses, and other observable behaviors can be used. RT is constrained by the speed of signal transmission in white matter as well as the processing efficiency of neocortical gray matter. Conclusions about information processing drawn from RT are often made with consideration of task experimental design, limitations in measurement technology, and mathematical modeling. Reaction time ('RT') is the time that elapses between a person being presented with a stimulus and the person initiating a motor response to the stimulus. It is usually on the order of 200 ms. The processes that occur during this brief time enable the brain to perceive the surrounding environment, identify an object of interest, decide an action in response to the object, and issue a motor command to execute the movement. These processes span the domains of perception and movement, and involve perceptual decision making and motor planning.