Reaction Time

REACTION TIME, the time from the moment of stimulation to the moment of the subject's reaction to this stimulation. It consists of a number of components, according to the number of elements of the reflex arc (according to Vogelsang, out of a reaction time of 0.239 seconds, 0.072 seconds fall to the sensory part of the arc, and 0.167 seconds to the motor part). Reaction time makes it possible to judge the speed with which cerebral processes proceed, expressing the duration of the conscious act of perception and the volitional impulse. It varies greatly among different subjects and can fluctuate in the same individual depending on various bodily states that alter the conditions of excitability of the central nervous system, such as fatigue, digestion, fluctuations in blood pressure, processes of external and internal inhibition, and the like. For visual perception, the reaction time is equal (on average) to 0.2 seconds. For various receptors (sense organs), threshold, i.e., minimally perceptible stimulations, yield more or less identical reaction times (0.33 seconds); as the intensity of the stimulus increases, the time first decreases and then remains unchanged (Exner's formula: v = a. log. J + C, where J is the illumination intensity, and a and C are constants). The shortest time is given by pain stimulation (0.116 seconds for the lower lip), and very prolonged times by temperature stimulations (for heat, 1.023 seconds). The reaction time is not identical for the same receptor on different areas of the body: for quinine on the tip of the tongue—1.082 seconds, and at its root—0.502 seconds. Sound stimuli yield the shortest reaction time at 33 vibrations (0.166 seconds). The degree of attention is of great importance in determining reaction time, and a source of errors can be "anticipation" (e.g., observed in astronomers, who mark the moment a star passes through the crosshairs of a telescope too early). With training, reaction time is shortened. When recognition or discrimination is introduced into the subject's task, the reaction time lengthens by approximately 0.03 seconds; the more complex the task, the greater the reaction time. An investigation of the time of laboratory-elaborated conditioned reflexes in dogs was also carried out: alimentary—0.08 seconds, defensive—0.06 seconds. Among pharmacological preparations, cocaine produces an acceleration, but at the same time an increase in the number of errors occurs. After the cessation of the narcotic effect of small doses of narcotics, acceleration is observed (chloral hydrate). Generally speaking, one and the same poison, depending on the dose, produces either a decrease or an increase in reaction time (e.g., caffeine), depending on the general excitatory or depressing effect of the given dose on the cerebral cortex. The determination of reaction time has great practical importance for the physiology of labor, psychotechnics, pedagogy, and the like.