The question of whether individuals are more prone to trust or to mistrust has increasingly interested economists and psychologists in recent years. To investigate whether people have an initial response tendency to trust versus mistrust, we developed a novel paradigm-the Dominant Behavior Measure (DBM). Capitalizing on decades of meticulous research in basic cognitive psychology (i.e., bilingual studies, Stroop paradigm), we designed a task to measure the dominance of reactions in the social realm. Participants engaged in a series of trust games that involved switching between trusting and mistrusting two trustworthy counterparts and two untrustworthy counterparts, identified by color (while ignoring a distractor name) or by name (when no color was presented). Like other dominant response tendencies (e.g., participant's first language), trust is faster, harder to switch to, and more interfering/facilitating than mistrust (Experiments 1-7). The dominance of trust holds in various social contexts-certainty of counterpart's un/trustworthiness (Experiments 4a-4c), unfamiliar counterparts (Experiments 5 and 6), counterparts from one's in-group versus out-group (Experiment 6), and negative framing of trust (Experiment 7)-showing that the dominant tendency to trust people (but not nonsocial objects, Experiment 8) is context-independent and robust. We rule out alternative explanations such as asymmetric payoff (Experiments 2 and 4b), familiarity and strength of association (Experiments 5 and 6), demand characteristics (Experiment 7), and positivity bias (Experiment 8). Introducing the DBM as a novel paradigm, we show that trust dominates mistrust and discuss the potential of this paradigm to determine dominant responses in manifold social domains. (PsycInfo Database Record (c) 2023 APA, all rights reserved).