Negation as conflict: Conflict adaptation following negating vertical spatial words.

In this study, we investigated whether the processing of negated directional terms such as "not up" or "not down" poses a conflict for participants and results in similar processing adjustments as non-linguistic conflicts do (Dudschig & Kaup, 2019). In each trial, participants read one of the following four phrases "now up", "not up", "now down" or "not down" and responded with a button press on a response key mounted in the upper versus lower vertical space. Behavioral data indicated that processing negated phrases leads to considerable processing difficulties for participants even after extensive practice. Interestingly, in line with standard conflict adaptation effects reported in the Simon, the Flanker and the Stroop task, negation processing was facilitated when preceded by another high conflict trial (i.e. a negated trial) as compared to a low conflict trial (i.e. an affirmative phrase). In addition, electrophysiological data showed that in negated trials first the to-be-negated information was activated (i.e., up in the case of "not up") and only in a second step, the outcome of the negation process was represented (i.e. down). In line with behavioral data, electrophysiological data was modified by trial sequence, suggesting negation triggering standard conflict adaptation patterns. Taken together, conflict-related processing adjustments can be also observed if the conflict is triggered by linguistic negation of vertical directional words. Implications of these findings are discussed.