A term frequently reported in PDD literature regarding the differences in responses to two types of questions. In Comparison Question Technique (QCT) formats, differential responsivity (differential reactivity) relates to the relative response magnitudes from relevant questions as compared to those from comparison questions. Within normal limits, this differential responsivity (reactivity) persists even when overall responsivity is attenuated, or as it habituates. For this reason, CQT formats are unlikely to render false negative decisions that are attributable to countermeasures that attack general arousals, such as the use of drugs, relaxation, or dissociation. By contrast, the Peak of Tension and Concealed Information Tests rely on differential responsivity (reactivity) between critical and neutral items. Decisions in these concealed information tests are based, not on the type of question that induces the response, but rather the presence or absence of significant responses to the critical items only. Therefore, the type of differential responsivity used in decision-making in PDD, along with vulnerability to certain types of countermeasures, will depend on the polygraph technique.