Despite the social importance of trust, studies show that humans are poor at explicitly distinguishing between when a person is lying versus telling the truth. However, people exhibit different physiological responses to lies versus truths. We propose that people unknowingly monitor their environments for deception, and such monitoring informs the degree to which those people expect others to be deceptive. Therefore, being in an environment of lies (vs. truths) would cause people to have less trust in others. We manipulated the environment by randomly assigning participants to watch videos of people (2, 4, 8, or 12) lying or telling the truth. Participants then read a paragraph about an individual (Bob) and rated how trustworthy he seemed. Participants rated Bob as less trustworthy after being exposed to lies (vs truths), suggesting that being in a deceptive environment might make people distrustful even if they don’t realize they are surrounded by liars.