Time taken to change the Speed of a Response

CRAIK 1 , in seeking to understand the nature of reaction times, questioned whether they were due to stimuli having to pass through a long chain of synapses between sense organ and effector, or whether some “condensed” time lag due to a decision process occurred in one part ot the chain. He argued that if the latter was the case, the process would be subject to serious interference from subsequent stimuli unless protected by a form of switching mechanism or “gate”. Subsequent experimental work 2 has indicated that the reaction time to a signal ( S 2 ) arriving during the reaction time to a previous signal ( S 1 ) is longer than when S 2 arrives well after the reaction to S 1 , and the theory (the “single-channel hypothesis”) has been advanced that the arrival of S 1 raises a “gate” which is not lowered until the reaction time to S 1 has ended. Reaction to S 2 is thus delayed by the time elapsing between the arrival of S 2 and the end of the reaction time to S 1 . Clear exceptions have been found only when it has been reasonable to regard subjects as able to group S 1 and S 2 into a single unit and respond to both together. Typically, this occurs only when they are less than about 0.1 sec apart, and not always then.