ABSTRACT
Recent studies attack the single-channel principle, which may be briefly stated as “a response is organised, and begun, before a second stimulus impinges upon the organizing centre” (Vince, 1948 a, p. 86) in two ways. Herman and Kantowitz (1970) argue that the single-channel model fails to account for changes in RT1 when S2 is presented, and that this is evidence for their “response—conflict” theory. Allport, Antonis, and Reynolds (1972) and Greenwald and Shulman (1973) report failures to observe the psychological refractory period (PRP) which is predicted to occur by single-channel theory. This study argues against “response—conflict” theory on the grounds that the effects on RT1 are due to processes which take place before the onset of S2, and that the limited range of the effect supports the single-channel model. A replication of Greenwald and Shulman’s (1973) study is undertaken which, by showing the typical PRP effect among subjects who did not “group” their responses, casts doubt on the interpretation of the above failures to find the PRP. Finally, a second experiment leads to the tentative suggestion that it is not feedback from a response which clears the channel (Welford, 1959), but execution of the program controlling the response.
