In everyday life, I am rarely asked how much a ball costs if a bat and a ball together cost $1.10 and the bat costs $1 more than the ball. However, as a psychologist, I have encountered such a situation. When I have, it has always been in a psychology class or a research paper.
In psychological research, many artificial questions and tasks like this are deliberately designed to elicit an incorrect response, which can then be interpreted as evidence of irrationality or bias — even if most people would never encounter such a situation in everyday life. This type of artificial task is part of the highly influential heuristics-and-biases research tradition. This approach to human decision-making investigates when heuristics (quick and often intuitive responses based on limited information) deviate from normative standards that are selected by researchers to define a rational response.
These deviations are commonly treated as evidence of cognitive bias: a systematic tendency of humans to make certain incorrect judgments. This is a preview of subscription content, access via your institution Receive 12 digital issues and online access to articles Prices may be subject to local taxes which are calculated during checkout Brady, O. et al. Dual-process theory and decision-making in large language models.
Psychol. 4, 777–792 (2025) Gigerenzer, G. How to make cognitive illusions disappear: beyond “heuristics and biases”. Psychol. 2, 83–115 (1991) Dhami, M.
K., Hertwig, R. & Hoffrage, U. The role of representative design in an ecological approach to cognition. Bull. 130, 959–988 (2004) Division of Ergonomics, Berlin Institute of Technology, Berlin, Germany School of Public Health, Imperial College London, London, UK The author has received fees from Flo Ltd, Qeios Ltd and MSD outside the submitted work.
The bat, the ball and the ecology of AI decision support. Nat Rev Psychol (2026). https://doi.org/10.1038/s44159-026-00627-1 DOI: https://doi.org/10.1038/s44159-026-00627-1
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