Delta plots with negative-going slopes as a potential marker of decreasing response activation in masked semantic priming

Delta plots with negative-going slopes (nDPs) reflect the phenomenon that an RT difference between two conditions is greater for relatively fast than for relatively slow responses. This unusual distributional pattern has predominantly been observed in the spatial Simon task, where it has been interpreted as reflecting the selective inhibition of an automatically activated response. The literature suggesting that a similar fading mechanism influences RTs in masked identity priming inspired us to check an analogous semantic priming paradigm for nDPs. Consistent with the findings in other paradigms, two masked semantic priming experiments revealed stronger priming effects for relatively fast than for relatively slow responses, thus reflecting an nDP. These findings are compatible with the ideas that the activation produced by masked semantic primes decreases over the course of a trial, such as that of irrelevant spatial information and of masked identity primes, and that nDPs are a general signature of within-trial decreases in response activation across different tasks and paradigms.