The conspiracy-effect  describes the finding that mere exposure to popular conspiracy theories can have a negative impact on pro-social decision-making and acceptance of established scientific principles. The term "conspiracy-effect" was coined by Sander van der Linden, a social-psychologist at Princeton University. The conspiracy-effect mainly refers to the idea that conspiracy theories are "sticky" and that even brief exposure to conspiratorial thinking may be sufficient to decrease civic engagement and cooperation in real-life social dilemmas, such as charitable giving, childhood vaccinations, support for actions that help reduce global warming and intentions to vote.
The finding is largely based on the fact that although public endorsement of popular conspiracy theories is growing, the majority of contemporary conspiracy theories lack credibility and scientific support and often propagate false information and harmful narratives. For example, recent research has found that espousal of some conspiracy theories may promote racist attitudes and political violence.
Research by Stephan Lewandowsky and colleagues  has shown that belief in conspiracy theories is associated with the "motivated rejection of science", including denial of the link between aids and HIV, smoking and lung cancer and CO2 emissions and global warming. Similar research has found that having people read articles about a particular conspiracy theory decreases inclinations to perform civic duties, such as intentions to vote and vaccinate.
- List of conspiracy theories
- Inoculation theory
- Merchants of doubt
- Misinformation effect
- Conspiracy theories
- van der Linden, Sander (2015). "The Conspiracy-Effect: Exposure to Conspiracy Theories (about Global Warming) Decrease Pro-Social Behavior and Science Acceptance". Personality and Individual Differences. 87: 171–173. doi:10.1016/j.paid.2015.07.045.
- Oliver, J.E., and Wood, T.J. (2014). "Conspiracy theories and the paranoid style(s) of mass opinion". American Journal of Political Science. 58: 952–966. doi:10.1111/ajps.12084.
- Clarke, S. (2002). "Conspiracy Theories and Conspiracy Theorizing". Philosophy of the Social Sciences. 32: 131–150. doi:10.1177/004931032002001.
- Viren, Swami. (2012). "Social psychological origins of conspiracy theories: The case of the Jewish conspiracy theory in Malaysia". Frontiers in Psychology. 3: 280. doi:10.3389/fpsyg.2012.00280.
- Lewandowsky, Stephan., Oberauer, K., and Gignac, G. (2013). "NASA faked the moon landing: Therefore, (climate) science is a hoax: An anatomy of the motivated rejection of science". Psychological Science. 24: 622–633. doi:10.1177/0956797612457686.
- Jolley, D., and Douglas, K.M. (2014). "The effects of anti-vaccine conspiracy theories on vaccination intentions". PLOS ONE. 9: e89177. doi:10.1371/journal.pone.0089177.
- Banas, John., and Miller, Gregory. (2013). "Inducing Resistance to Conspiracy Theory Propaganda: Testing Inoculation and Metainoculation Strategies". Human Communication Research. 39: 184–207. doi:10.1111/hcre.12000.