Further confirmation of same vs. different processing differences

Two four-digit numbers were matched in a "same-different" reaction time paradigm. In the "all-same" condition, the subject responded same if all digits matched and different otherwise. In the "all-different" condition, the subject responded same if at least one digit matched and different 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.