Abstract
People rate and judge repeated information more true than novel information. This truth-by-repetition effect is of relevance for explaining belief in fake news, conspiracy theories, or misinformation effects. To ascertain whether increased motivation could reduce this effect, we tested the influence of monetary incentives on participants’ truth judgments. We used a standard truth paradigm, consisting of a presentation and judgment phase with factually true and false information, and incentivized every truth judgment. Monetary incentives may influence truth judgments in two ways. First, participants may rely more on relevant knowledge, leading to better discrimination between true and false statements. Second, participants may rely less on repetition, leading to a lower bias to respond “true.” We tested these predictions in a preregistered and high-powered experiment. However, incentives did not influence the percentage of “true” judgments or correct responses in general, despite participants’ longer response times in the incentivized conditions and evidence for knowledge about the statements. Our findings show that even monetary consequences do not protect against the truth-by-repetition effect, further substantiating its robustness and relevance and highlighting its potential hazardous effects when used in purposeful misinformation.
Highlights
People see, read, and hear many different facts and statements each day, which they can believe or doubt
People use repetition as a cue to make this judgment; believing repeated statements more compared with nonrepeated statements, a phenomenon known as the illusory truth effect, a truth-by-repetition effect, or a truth effect (Brashier & Marsh, 2020; Unkelbach et al, 2019)
There was no significant main effect for incentives, Mhigh = 0.579, SDhigh = 0.148, Mmed = 0.564, SDmed = 0.145, Mno = 0.565, SDno = 0.127, F(2, 318) = 0.40, p = .669, ηp2 = .003, and neither the knowledge effect nor the repetition-induced truth effect interacted with the incentives condition, F(2, 318) = 2.25, p = .107, ηp2 = .014, and F(2, 318) = 2.07, p = .128, ηp2 = .013, respectively
Summary
We had no a priori estimate for the effect size of monetary incentives; we pragmatically aimed for 100 participants per condition as an established threshold in our lab (i.e., smaller effects are too costly to investigate). We recruited 321 participants on campus (Mage = 23.09 years, SD = 6.84; 180 female, 141 male) who participated in exchange for 4€ plus a potential bonus in the incentivized conditions. In the two incentivized conditions, participants could earn up to 12€ (high incentives condition) or 6€ (medium incentives condition), but we recruited all participants with the expectation of receiving 4€. They were randomly assigned to the high incentives, medium incentives, and no incentives conditions. Half of the statements were factually true and half factually false; the other half only appeared in the judgment phase. Participants judged 30 true-old, 30 false-old, 30 true-new, and 30 falsenew statements
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