Combining Order and Consistency Effects in Two-Sided Messages on the Non-Effectiveness of Homeopathy

How do people whose beliefs conflict with the scientific consensus respond to two-sided messages that communicate both the belief-challenging consensus and isolated belief-affirming findings? Across three experiments (N_total = 1,124), we gave homeopathy supporters belief-challenging and belief-affirming information in varying orders. In Studies 1 and 2, we measured perceived trustworthiness of homeopathy-related science between both pieces of information. Compared with participants who received belief-challenging information first, participants who received belief-affirming information first reported higher trust in homeopathy-related science after the first information and were more likely to report believing that homeopathy is not effective after both pieces of information. Study 3 showed that the order effect on reported belief in the effectiveness of homeopathy did not occur without the interim measurement of perceived trustworthiness. This pattern is consistent with a consistency effect due to the interim measurement. Overall, two-sided messages did not outperform one-sided messages regarding changes in reported beliefs.