Pathogens Are Linked to Human Moral Systems Across Time and Space

Abstract

Infectious diseases have been an impending threat to the survival of individuals and groups throughout our evolutionary history. As a result, humans have developed psychological pathogen-avoidance mechanisms and groups have developed societal norms that respond to the presence of disease-causing microorganisms in the environment. In this work, we demonstrate that morality plays a central role in the cultural and psychological architectures that help humans avoid pathogens. We present a collection of studies which together provide an integrated understanding of the socio-ecological and psychological impacts of pathogens on human morality. Specifically, in Studies 1 (2,834 U.S. counties) and 2 (67 nations), we show that regional variation in pathogen prevalence is consistently related to aggregate moral Purity. In Study 3, we use computational linguistic methods to show that pathogen-related words co-occur with Purity words across multiple languages. In Studies 4 (n = 513) and 5 (n = 334), we used surveys and social psychological experimentation to show that pathogen-avoidance attitudes are correlated with Purity. Finally, in Study 6, we found that historical prevalence of pathogens is linked to Care, Loyalty, and Purity. We argue that particular adaptive moral systems are developed and maintained in response to the threat of pathogen occurrence in the environment. We draw on multiple methods to establish connections between pathogens and moral codes in multiple languages, experimentally induced situations, individual differences, U.S. counties, 67 countries, and historical periods over the last century.

Morality Beyond the WEIRD: How the Nomological Network of Morality Varies Across Cultures

“…In addition, using Muthukrishna's (2020) newly validated index of WEIRDness cultural distance, we tested novel predictions about different moral foundations in non-WEIRD cultures, finding that Purity and Loyalty are particularly higher in less WEIRD populations such as Egypt and Saudi Arabia. Our approach has important implications for moral psychological research because moral cognition may be more a kludge, shaped by local social norms and socio-ecological factors (Atari, Reimer, et al, 2021) and other features of cognition than a unified cognitive architecture (Stich, 2006), hence it is imperative that our tools are created with this human diversity in mind, making sure that our tools are understandable and usable across less-WEIRD populations. In addition to collecting data from many different populations, we also maximized, as much as possible, religious diversity in our sample.…”

The (Moral) Language of Hate

“…We would also like to acknowledge that the concept of moral purity, even though predictive of various real-world behaviors (e.g., Atari, Reimer, et al, 2022;Reimer et al, 2022), is complex and may be multifaceted (Gray et al, 2022). With that said, our work is a clear illustration for the value of a pluralist-descriptive approach to human morality -one that is not confined to normatively endorsed foundations in the West (Atari, Haidt, et al, 2022).…”

“…The cosine similarities of each hateful term with words from a given MFD category were averaged, yielding a single (average) similarity score per MFD category, language, and hateful term. Using word embeddings' cosine similarity between two different categories of words in order to determine the "loading" of one onto the other is a practice established in prior research (Atari, Reimer, et al, 2022; 10 https://fasttext.cc/docs/en/crawl-vectors.html Garg et al, 2018;Garten et al, 2018;Kozlowski et al, 2019;Lucy et al, 2020).…”

Historical Psychology

“…Although our inability to experimentally manipulate or unobtrusively observe historical participants places some limits on what we can infer from these (potentially decontextualized) data, traces of human thought can be a rich and informative source of descriptive information on past psychology. Of course, research can test theories about the drivers of psychological change using contemporary experimental psychological studies, and then enrich and generalize such insights using historical evidence, looking for convergence (e.g., Atari et al, 2021). Large-scale analysis of textual data is an exciting new area of research with great promise for historical psychology.…”