Simple reaction time (SRT) measures the interval between a single stimulus onset and a single predetermined motor response. Because no stimulus discrimination or response selection is required, SRT reflects the baseline speed of neural transmission and motor execution. Adults typically average 150-250ms.
Definition and Measurement Principle
Simple reaction time (SRT) measures how quickly a person responds to a single, predetermined stimulus with a single, predetermined action. A classic example is pressing a button the moment a light appears on screen. Since no discrimination between stimuli is needed, SRT captures the shortest possible path from perception to motor output. The measured value encompasses peripheral nerve conduction velocity, synaptic transmission efficiency, and muscle contraction onset time.
Typical Values and Sources of Variation
In healthy adults, SRT is considered shorter for auditory stimuli than for visual stimuli. Factors influencing individual differences include age, arousal level, body temperature, and caffeine intake. SRT lengthens with age, and one study reported that this increase is due primarily to slowed motor output. A circadian pattern also exists.
Applications and Limitations in Cognitive Testing
MyRank's Reaction Time Test measures SRT. In the subtraction method, SRT is subtracted from choice reaction time to estimate the time taken by stimulus discrimination and response selection. An unusually slow SRT may indicate sleep deprivation or attentional lapses. However, SRT captures only one facet of cognitive performance. Additionally, anticipatory responses - where participants press the button before the stimulus appears by learning timing patterns - can contaminate measurements, and randomized inter-stimulus intervals are used to reduce this contamination.