As the climate crisis accelerates, extreme heat events are becoming more frequent, intense, and prolonged. While their impacts on physical health are well established, evidence on how heatwaves affect human cognition, social functioning, and collective well-being remains fragmented and inconsistent. Moreover, the consequences of extreme heat are expected to vary substantially: individuals differ in their exposure to extreme heat, their sensitivity, and their capacity to adapt and protect themselves.
In this talk, we introduce the Heat & Cognition ManyLabs Project, an ongoing global three-wave natural experiment leveraging real-world extreme heat events to examine their impact on cognition and collective well-being. Using a Big Team Science (BTS) approach, we aim to collect data from more than 50,000 participants across 40+ cities worldwide. This unique design allows us to capture contextual variability and to identify which aspects of vulnerability moderates heat's effects on the human mind.
The central focus of this talk is our development of a heat vulnerability index, proposing a multi-dimensional framework including exposure (e.g. temperature, humidity, perceived heat stress), sensitivity (e.g. age, gender, and health status), and adaptive capacity (e.g. access to green spaces, housing conditions, and protective behaviors).
We will present the key indicators of this index, discuss conceptual and methodological challenges in its development, and outline how vulnerability can be systematically integrated as a moderator in analyzing cognitive, social, and well-being outcomes. Finally, we highlight the policy relevance of the expected results, particularly considering the adaptive capacity dimension, which directly translates into actionable protection measures for cities and communities. In doing so, the project exemplifies applied psychology at the intersection of climate science, public health, and social policy.