A new study has found that high temperatures do not make people more selfish or less cooperative in economic decisions, challenging assumptions that heat directly fuels aggression or reduces prosocial behaviour.
Researchers led by Alessandra Cassar invited university students from five countries, Colombia, India, Kenya, Mexico, and the US, to take part in economic games designed to measure sharing behaviour and decision making.
Participants made choices about whether to share payoffs with others, whether to reduce another player’s payoff at a personal cost as a measure of spite, and whether to compete with other players. Some participants were first exposed to stress by losing a competitive game.
The central experimental manipulation involved temperature. Some participants played in cool rooms set at 18°C, while others played in hot rooms that reached up to 34°C.
When temperatures rose above 30°C, participants reported significantly higher levels of frustration, tiredness, and unhappiness, indicating clear thermal discomfort and negative emotional states.
Despite these effects on mood, the researchers found no systematic impact on behaviour. Heat and prior stress from losing a game did not significantly influence egalitarianism, resource maximisation, selfishness, spite, or competitiveness.
The findings suggest that although heat produces physiological and emotional strain, it does not directly alter these aspects of economic decision making or prosocial tendencies in laboratory settings.
The study did reveal consistent patterns related to gender and culture.
Women showed more egalitarian behaviour than men across all five countries. Women were also less competitive than men in every country except Kenya.
Cultural differences also appeared in specific dimensions of prosociality. Participants from the US placed less emphasis on equal outcomes between players than participants from the other countries. However, US participants showed greater concern for maximising the total payout to both players, even when the distribution was uneven.
The authors note that their findings do not rule out broader societal effects of heat. High temperatures can indirectly influence violence or conflict by damaging crops, straining social systems, or increasing alcohol consumption.
However, the results indicate that heat alone does not directly promote selfishness or reduce cooperation at the individual level in economic interactions.
The cross-cultural laboratory approach provides insight into concerns surrounding rising global temperatures and social stability. Previous research has linked hotter climates to higher rates of violence at the societal level, but this study suggests that such patterns are unlikely to arise from immediate changes in individual prosocial or competitive preferences.
Future studies could examine whether prolonged heat exposure, real-world environments, or combinations of stressors produce different behavioural outcomes.