Repetition can make even the most bizarre claims seem more true

The spread of misinformation over recent years poses huge dangers, and has so far proven extremely difficult to bring under control. Psychological research has revealed much of what brings people to believe false information, but the full picture is still far from complete, and new findings are bringing to light yet more factors that may maintain this problem.

One example is the Truth-by-Repetition (TBR) effect — that repeating a statement increases how true it's perceived to be. A prominent theory for why this happens emphasises the role of "processing fluency"; in essence, repetition makes the information easier to cognitively process, and this ease is misinterpreted as a signal that the information is true.

Until recently, this phenomenon was thought to be limited to statements which could conceivably be true. But new research suggests that the effect extends much further, and can make even outlandish claims seem more truthful.

Past work in the field had found that a single repetition of nonsensical claims like "The Earth is a perfect square" didn't influence how true such statements were perceived to be. But this may have been because the methods weren't sensitive enough to spot a small effect.

To remedy this, Doris Lacassagne and colleagues at UCLouvain in Belgium showed participants more false statement repetitions than previous studies, and also had them respond on a scale with a substantially greater number of discrete ratings. Their recent study involved 232 English-speaking, US-based participants (51% female), recruited online.

In the first phase of the experiment, these participants were presented with eight of a possible 16 statements rated as very implausible by participants from a previous study. These included outlandish claims such as "Elephants weigh less than ants" and "Smoking is good for your lungs", as well as perhaps more plausible claims (at least for an American sample) such as "Rugby is the sport associated with Wimbledon."

Participants were asked to rate how interesting they found the eight presented statements, and were advised that they may be asked to rate the same statement multiple times. These statements were presented randomly, and repeated five times each, resulting in 40 trials overall.

Immediately after this, participants were randomly shown all 16 statements — eight of which they had seen repeatedly in the previous phase, and eight of which were new. They were asked to rate how true they felt each statement was, on a scale from −50 ("definitely false") to +50 ("definitely true").

Analyses of responses showed that repeating the implausible statements influenced participants' truth ratings. While all ratings of truthfulness were still well into negative territory, statements that had been shown repeatedly were overall perceived to be less false than newly presented statements. Statements that were arguably less extreme (but still highly implausible), such as "A monsoon is caused by an earthquake", were most subject to TBR effects.

Further digging also uncovered distinct patterns between participants: 53% showed a positive TBR effect, with their ratings sliding towards truth after statements were repeated, whereas 19% showed no effect, and the remaining 28% showed a negative TBR effect. In this latter group, repetition served to make the statements seem even more implausible. These analyses suggest that not everyone responds to the TBR effect in the same manner.

These findings demonstrate that a surprisingly low number of repetitions can affect the perceived truth of highly implausible statements. This challenges some theories that suggest enhancing feelings of fluency should only make statements seem true if they are plausible.

Further probing into individual differences, particularly why some participants found statements less truthful with repetition, could yield fascinating insights into how fluency of information is interpreted by different people. More longitudinal studies could also be informative. Shifts in truth perceptions were relatively small after a few, tightly spaced repetitions — investigating how this effect might shape perceptions of truth over days and weeks may help us better understand how the TBR effect works in day-to-day life.

In the era of the 24-hour repeating news cycle and online algorithms, the TBR effect gives us some insight into why and how people come to believe increasingly incredible claims. With luck, these findings will be a piece of the wider puzzle in finding more robust ways to prevent misinformation spreading.

Further reading

– Is Earth a perfect square? Repetition increases the perceived truth of highly implausible statements

About the author

Post written for BPS Research Digest by Emma L. Barratt (@E_Barratt). Emma is a cognitive scientist and science communicator based in Newcastle, UK. Her work centres primarily around atypical and clinical psychology, as well as cognitive factors pertaining to human spaceflight and space exploration. In 2015, she published the first peer reviewed investigations of Autonomous Sensory Meridian Response. She also works alongside an international team to produce educational content for the popular YouTube channel SciShow.