Psychological Refractory Period

The psychological refractory period is a measurable delay in a person's response to a second of two stimuli presented in close succession, occurring specifically when the response to the first stimulus is still being planned or carried out at the moment the second stimulus arrives, so that the second response is held up until processing capacity frees up rather than being produced immediately. Researchers study the effect using dual-task paradigms in which participants must respond separately and as quickly as possible to two different stimuli presented with a short, experimentally varied gap between them, consistently finding that response time to the second stimulus lengthens as that gap shrinks, a pattern the British psychologist Alan Welford helped establish and explain in influential research published in the early 1950s. The phenomenon is widely interpreted as evidence for a central attentional or decision-making bottleneck in human cognition, a single-channel stage involved in selecting and preparing a response that can only fully process one task's response at a time even when two separate stimuli have already been perceived and identified in parallel. Because it isolates a specific limitation in dual-task performance under the tightly controlled and quantifiable conditions of a laboratory task, the psychological refractory period remains one of the most extensively used paradigms for studying the underlying architecture of human attention and multitasking.