Understanding population-level variability in who responds more strongly to pathogen threats is important for devising strategic health-based risk messages targeted at ideologically diverse populations. The aims of this dissertation were to investigate how politically polarized responses to COVID-19 changed over time, the role of political elite cues in shaping responses to COVID-19 and other pathogens, and whether such effects depend on individual differences such as disgust sensitivity and moral feelings about purity. Using a longitudinal probability-based U.S. nationally representative NORC AmeriSpeak sample measured in March-April, 2020 (N = 6,514) then six months later in September-October, 2020 (N = 5,661), Study 1 demonstrated that COVID-19 fear, perceived COVID-19 death risk, and health-protective behaviors became increasingly polarized over time. Initial differences between Democrats and Republicans diverged over the first six months of the pandemic, as did responses among Republicans by support for former president Donald Trump. Trump Republicans initially reported less COVID-19 fear and health-protective behaviors than non-Trump Republicans, and these differences became more pronounced over time. Importantly, there were minimal differences by political identity, and none by Trump support, in perceived infection risk of a non-politicized pathogen: the seasonal flu. To examine causality, Study 2 tested whether responses to an ostensibly real superbacteria, described as starting to spread internationally in a mock online Associated Press article, can be experimentally polarized via divergent political elite messages. In an online Prolific sample (N = 400) there was a negative partisanship effect where Republicans felt less threatened by the superbacteria when Democratic leaders cued worry about it and Republican leaders downplayed it, but not vice versa. In another U.S. nationally representative NORC AmeriSpeak sample (N = 1,947), Study 3 replicated this effect showing that pathogen disgust sensitivity predicted stronger perceived superbacteria threat regardless of political elite cues, while the effect of moral purity was nuanced. These results have theoretical implications for understanding the evolutionary roles of ingroup authority, disgust sensitivity, and moral purity in pathogen threat responses. These findings also suggest that political elite messages and emotional and moral sensitivities of the target audience be simultaneously considered when devising public health pathogen-related risk communications.

During a contentious primary campaign, people may argue passionately against a candidate they later support during the general election. How do people reconcile such potentially conflicting attitudes? This study followed 602 United States citizens, recruited from Amazon Mechanical Turk, at three points throughout the 2016 presidential election investigating how attitudes and preferences changed over time and how people remembered their past feelings. Across political parties, people’s memory for their past attitudes was strongly influenced by their present attitudes; more specifically, those who had changed their opinion of a candidate remembered their past attitudes as being more like their current attitudes than they actually were. Participants were also susceptible to remembering false news events about both presidential candidates. However, they were largely unaware of their memory biases and rejected the possibility that they may have been susceptible to them. Not remembering their prior attitude may facilitate support of a previously disliked candidate and foster loyalty towards a party nominee during a time of disunity by forgetting they ever used to dislike the candidate.