Evidence of a Single-Channel Decision Mechanism Limiting Performance in a Serial Reaction Task

Abstract

An experiment is described in which the subject sat facing a display of two neon bulbs. When the left-hand bulb lit he pressed a key under his left hand, and when the right hand bulb lit he pressed a key under his right hand. The left-hand bulb gave brief flashes at random intervals averaging about 4 sec. The right-hand bulb gave a brief flash at regular intervals of about 4 sec. The experiment repeats (the author believes for the first time) certain essential conditions of Vince's (1948, 1950) experiments and, following detailed scrutiny of every pair of responses, is taken as evidence for the following statements:— (a) The response to a signal arriving during the reaction time to a former signal will be delayed by an amount approximately equal to the time elapsing between the arrival of the signal and the end of the reaction time to the former signal. (b) An exception to this may occur when two signals arrive close together. In this case the two signals may be responded to as a single group. (c) Delays can be occasioned by the monitoring of responses as well as by reactions to signals. (d) “Grouping” of signal and monitoring may occur when a signal arrives close to the beginning of the movement made in response to a previous signal. A survey is made of current theories in this field and suggestions given for further research.