Matching bias refers to the non-normative performance that occurs when elements mentioned in a rule do not correspond with those in a test item. One aim of the present work is to capture matching bias via reaction times as participants carry out truth-table evaluation tasks. Experiment 1 requires participants to verify conditional rules, and Experiment 2 to falsify them as the paradigm employs four types of conditional sentences that systematically rotate negatives in the antecedent and consequent; and presents predominantly (...) cases having true antecedents. These experiments reveal that mismatching is linked to higher rates of incorrect responses and slower evaluation times. A second aim is to investigate the way not is processed. We compare a narrow view of negations, which argues that negation only denies information, to a search for alternatives view, which says that negations function to prime appropriate alternatives. Findings from both experiments support a narrow reading view. (shrink)