Unveiling the boost in the sandwich priming technique

The masked priming technique (e.g., #####-house-HOUSE) is the gold-standard tool to examine the initial moments of word processing. Lupker and Davis (2009) showed that adding a pre-prime identical to the target produced greater priming effects (sandwich technique: #####-HOUSE-house-HOUSE). While there is consensus that the sandwich technique magnifies the size of priming effects relative to the standard procedure, the mechanisms underlying this boost are not well understood (i.e., does it reflect quantitative or qualitative changes?). To fully characterize the sandwich technique, we compared the sandwich and standard techniques by examining the RTs and their distributional features (delta plots; conditional-accuracy functions), comparing identity vs. unrelated primes. Results showed that the locus of the boost in the sandwich technique was two-fold: faster responses in the identity condition (via a shift in the RT distributions) and slower responses in the unrelated condition. We discuss the theoretical and methodological implications of these findings.