The causal effect of a health treatment on beliefs, stated preferences and memories.

The paper estimates the causal effect of a health treatment on patients' beliefs, preferences and memories about the treatment. It exploits a natural experiment which occurred in the United Kingdom during the COVID-19 vaccination campaign. UK residents could choose to opt into the vaccination program, but not which vaccine they received. The assignment to a vaccine offered little objective information for learning about its qualities, but triggered strong psychological demand for reassuring beliefs. We surveyed a sample of UK residents about their beliefs on the different COVID-19 vaccines before and after receiving their jab. Before vaccination, individuals exhibit similar prior beliefs and stated preferences about the different vaccines. After vaccination, however, they update their beliefs overly optimistically about the safety and effectiveness of the vaccine they received, state that they would have chosen it if they could, and have distorted memories about their past beliefs. These results cannot be explained by conventional experience effects. At the aggregated level, they show that random assignment to a health treatment predicts a polarization of opinions about its quality. At the individual level, these findings provide evidence in line with the predictions of motivated beliefs and over-inference from weak signals in a real-world health setting.

Unethical amnesia responds more to instrumental than to hedonic motives.

Humans care about morality. Yet, they often engage in actions that contradict their moral self. Unethical amnesia is observed when people do not remember or remember less vividly these actions. This paper explores two reasons why individuals may experience unethical amnesia. Forgetting past unethical behavior may be motivated by purely hedonic or affective reasons, such as the willingness to maintain one's moral self-image, but also by instrumental or strategic motives, in anticipation of future misbehavior. In a large-scale incentivized online experiment (n = 1,322) using a variant of a mind game, we find that hedonic considerations are not sufficient to motivate the forgetting of past cheating behavior. This is confirmed in a follow-up experiment (n = 1,005) in which recalls are elicited the same day instead of 3 wk apart. However, when unethical amnesia can serve as a justification for a future action, such as deciding on whether to keep undeserved money, motivated forgetting is more likely. Thereby, we show that motivated forgetting occurs as a self-excuse to justify future immoral decisions.