Further confirmation ofsame vs.different processing differences

Two four-digit numbers were matched in a “same-different” reaction time paradigm. In the “all-same” condition, the subject respondedsame if all digits matched anddifferent otherwise. In the “all-different” condition, the subject responded same if at least one digit matched anddifferent if all digits differed. In either condition, the number of matching digits ranged from zero to four. The all-same results supported previous work: the fewer the number of mismatches, the slower the response, except that zero mismatches resulted in a response faster than one mismatch. These findings have been taken as supporting a two-process model: an identity detector mechanism and a self-terminating feature-matching process. An alternative one-process model could explain the results by assuming that the “same” response is primed during the match process. However, the all-different results showed reaction time to be a monotonie function of the number of matching digits. Such a finding contradicted the priming model and supported a two-process model.