Two separate blocks (habituation and test) of trials consisting of 24 slides each were presented using procedures similar to those used in previous studies (Cuthbert et al., 1996). Within each session, the blocks included 6 slides of each type (positive, negative, neutral, cigarette). Each slide was presented for 6 s followed by a randomly determined interslide interval that varied from 10 to 20 s. The order of slide presentation was counterbalanced, so that within a session, participants saw each picture equally often in the first through sixth positions within each block, and each block occurred first or second with equal frequency. Four separate slide orders, one for each session, were counterbalanced across subjects, though the slides were the same for each session. The procedure took approximately 45 min.
