Broken Physics: A Conjunction-Fallacy Effect in Intuitive Physical Reasoning

Ethan Ludwin-Peery, Neil R. Bramley, Ernest Davis, Todd M. Gureckis

Research output: Contribution to journalArticlepeer-review


One remarkable aspect of human cognition is our ability to reason about physical events. This article provides novel evidence that intuitive physics is subject to a peculiar error, the classic conjunction fallacy, in which people rate the probability of a conjunction of two events as more likely than one constituent (a logical impossibility). Participants viewed videos of physical scenarios and judged the probability that either a single event or a conjunction of two events would occur. In Experiment 1 (n = 60), participants consistently rated conjunction events as more likely than single events for the same scenes. Experiment 2 (n = 180) extended these results to rule out several alternative explanations. Experiment 3 (n = 100) generalized the finding to different scenes. This demonstration of conjunction errors contradicts claims that such errors should not appear in intuitive physics and presents a serious challenge to current theories of mental simulation in physical reasoning.

Original languageEnglish (US)
Pages (from-to)1602-1611
Number of pages10
JournalPsychological Science
Issue number12
StatePublished - Dec 2020


  • inference
  • intuitive physics
  • open data
  • open materials
  • prediction
  • preregistered
  • reasoning

ASJC Scopus subject areas

  • General Psychology


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