PT - JOURNAL ARTICLE AU - Jiang, Yaoguang AU - Huttunen, Annamarie AU - Belkaya, Naz AU - Platt, Michael L TI - Monkeys Predict US Elections AID - 10.1101/2024.09.17.613526 DP - 2024 Jan 01 TA - bioRxiv PG - 2024.09.17.613526 4099 - http://biorxiv.org/content/early/2024/09/19/2024.09.17.613526.short 4100 - http://biorxiv.org/content/early/2024/09/19/2024.09.17.613526.full AB - How people vote often defies rational explanation. Physical traits sometimes sway voters more than policies do–but why? Here we show that rhesus macaques, who have no knowledge about political candidates or their policies, implicitly predict the outcomes of U.S. gubernatorial and senatorial elections based solely on visual features. Given a pair of candidate photos, monkeys spent more time looking at the loser than the winner, and this gaze bias predicted not only binary election outcomes but also the candidates’ vote share. Analysis of facial features revealed candidates with more masculine faces were more likely to win an election, and vote share was a linear function of jaw prominence. Our findings endorse the idea that voters spontaneously respond to evolutionarily conserved visual cues to physical prowess and that voting behavior is shaped, in part, by ancestral adaptations shared with nonhuman primates.Significance Statement We report that monkeys and humans alike respond spontaneously to evolutionarily conserved facial masculinity cues in political candidates, and this innate sensitivity partly shapes voting behavior, highlighting the imperative for voters to overcome this ancient heuristic by becoming more informed on candidates and their policies.Competing Interest StatementThe authors have declared no competing interest.