If you hear a statement repeatedly, you’re more likely to believe it’s true—even if it isn’t. This phenomenon is known as the illusory truth effect, a cognitive bias where repeated statements are perceived as more truthful than new ones. In today's media landscape—where the same information is often presented repeatedly through posts, shares, and reposts—this effect has become increasingly relevant. 

Students in Emily Cohen-Shikora’s Spring 2024 Experimental Psychology class got interested in the illusory truth effect and decided to investigate it for their independent project. As a class, they tested a whether presenting a short educational video followed by a quiz on the illusory truth effect, and a warning that they should try to avoid the effect, might reduce or eliminate it. To maximize realism, the students collected trivia statements and edited them to look like news-style headlines from seemingly trustworthy sources. Their educational intervention was delivered via short-form Tik Tok videos, both to promote active processing of information and to reflect the common information-consumption patterns on social media platforms. The intervention worked surprisingly well, effectively eliminating the bias in a sample of WashU students. This was a striking finding because few prior studies had successfully eliminated the effect—most had only reduced the effect. 

Inspired by these results, a subgroup of students from the class, led by Dr. Emily Cohen-Shikora, graduate student Jennifer Shearon, and senior undergraduate Zonghua (Cathy) Shi, extended the study to further investigate the elimination effect across population and conditions. They conducted a follow-up study with a more general population sample with a wide age range. Once again, the intervention successfully eliminated the ITE in the experimental group. In a third study, the team added a one-day delay between the video intervention and the truth-rating task in a third study. Even with the delay, participants who received the intervention continued to be immune to the bias, while control groups showed a robust illusory truth effect. 

The student-led research team wrote the results up for publication, and recently learned that their paper has been accepted for publication in Applied Cognitive Psychology. The findings were also featured at the Fall 2024 WashU Arts & Sciences Undergraduate Research Symposium and presented at the 65th Annual Meeting of The Psychonomic Society. 

“It’s really meaningful to see that we have made progress in understanding the Illusory Truth Effect,” said senior Cathy Shi, first author of the paper. “Our study may point the way for future researchers and policymakers. But honestly, the most exciting part was how it all started from a regular class project.”