**Principal investigator:** **Scott Radnitz** University of Washington Email: srad@u.washington.edu Homepage: http://faculty.washington.edu/srad/ **Sample size:** 1997 **Field period:** 5/2/2011-9/2/2011 **Abstract:** Why do people believe in conspiracy theories? Most explanations in the American political context involve demographic factors or partisan attachments, but their utility is limited because they deal with conspiracies that are closely linked to pre-existing attitudes and therefore struggle to identify the mechanisms behind conspiratorial belief in general. This study investigates both the attributes of people who are likely to believe in conspiracy theories, and the general properties of conspiratorial conjectures that make them more credible. Through an Internet-based survey experiment, I tested several hypotheses about what makes people more likely to perceive a conspiracy: whether they are in a calm or anxious state of mind; whether the putative conspirator is a government or corporation; whether the putative victim is named or left anonymous; and whether factual information changes opinions. **Hypotheses:** 1) Exposure to a prime intended to induce anxiety will increase the likelihood that Rs perceive the fictional scenario as a conspiracy. 2) Determination of culpability of the perpetrator will depend on political affiliations—corporations will be more likely to be seen as conspirator for liberals/Democrats and government as conspirator for conservatives/Republicans. 3) An individual, named victim will be more likely associated with a conspiracy than multiple, unnamed victims. 4) Agnostic as to the degree to which Rs can be persuaded to believe or disbelieve in a conspiracy. **Experimental Manipulations:** The survey includes a fictional “conspiracy vignette” disguised as a newspaper article excerpt, which excludes references to actual actors and events that could trigger partisan or ideological responses. The mock article describes a mysterious illness with flu-like symptoms that afflicts a small town. I vary the identity of the putative perpetrator (government or corporate laboratory) and victims (individual and named or multiple and nameless). Rs are also randomly assigned a “macroeconomic anxiety prime” and a “factual” statement that challenges their assessment of whether the event was a conspiracy, which is adaptive to their responses: Rs who tended toward conspiracy thinking received a “mitigating” factual statement, while ones who did not see a conspiracy received an “insinuating” one. **Key Dependent Variables:** I measure the dependent variable—belief in conspiracy—with five questions: the degree to which the respondent feels sympathy for the victim(s), whether there is a connection between the company/government and the victim, whether the company/government “did something wrong” or “is hiding something,” and whether the respondent would support an investigation into the government/company’s responsibility for the illness. **Summary of Findings:** Overall, responses tended toward the “conspiratorial” end of the spectrum. The most insinuating combination of treatments was the macroeconomic prime, corporation, and multiple victims. The least conspiratorial version was no prime, government, and the individual victim. For the manipulations, the results were as follows: First, the anxiety prime was significantly associated with conspiracy perceptions. Second, corporations were more likely than the government to be seen as a conspirator. Third, counter to expectations, people were consistently more likely to see a conspiracy when numerous but nameless people died from the illness and nameless victims elicited more sadness than the named victim. Fourth, the effect of the factual statement on belief was fairly large, and people were more likely to move in a more, rather than less, conspiratorial direction.