Observations on the microstructure of response conflict.

Three experiments are detailed which indicate the usefulness of the frequency of double responses (DRs) as an indicant of response conflict, in addition to the usual RT measures. DRs are responses on which an initial (often partial) error response is made that is rapidly amended to a correct response. Such responses occur most frequently in stimulus conditions where response conflict is expected by theory to be present and is indicated by changes in RT. Partial activation of competing responses has been demonstrated before using physiological measures (Coles, Gratton, Bashore, C. W. Eriksen, & Donchin, 1985; C. W. Eriksen, Coles, Morris, & O'Hara, 1985) when both responses could physically be made at the same time. DRs seem to be an equivalent type of movement when the subject cannot physically make but one movement at a time. The usefulness of this index of response conflict lies in its ease of implementation.