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The Rest Is Science
The Rest Is Science

The Reasoning Test Psychologists Still Can't Explain

April 20, 2026 • 1h 2m

Summary

⏱️ 10 min read

Overview

Michael Stevens and Hannah Fry explore the famous Wason Selection Task, a reasoning puzzle that 96% of people fail, despite it being logically simple. Through various formulations of the same logical problem, they reveal how human reasoning evolved for social cooperation rather than abstract truth-finding. The discussion covers confirmation bias, the difficulty of seeking counterexamples, and why we're better at solving problems involving social rules than mathematical abstractions.

Introduction to Reasoning and Podcast Setup

Michael Stevens and Hannah Fry open the episode by establishing the context for discussing a challenging reasoning task. Michael expresses confidence that Hannah might succeed where most people fail, while noting that providing advance warning might actually help performance compared to standard experimental conditions where participants receive no special preparation.

  • Michael introduces a test that basically everyone fails, though he suspects Hannah might do well
  • In actual experiments, people just show up for compensation without special preparation
  • Advance warning and emphasis on difficulty might cause people to think more carefully and improve performance

The Wason Selection Task: A Puzzle Almost Everyone Gets Wrong

Michael introduces the classic Wason Selection Task from 1966, presenting Hannah with four cards (A, G, 7, 8) and asking which ones need to be turned over to verify the rule 'if there's an A on one side, there's a 7 on the other.' Hannah initially almost falls into the trap but correctly identifies that you need to check the A and the 8 cards. This deceptively simple puzzle has only a 4-10% success rate, making it one of the most researched problems in the psychology of reasoning.

  • The Wason Selection Task was developed in 1966 and has been called the most intensely researched single problem in the history of reasoning
  • In the original test, only 10% of people got it right; across all studies, the success rate is closer to 4%
  • The correct answer is to turn over the A card and the 8 card - you need to check for both confirmation and counterexamples
  • 46% of people incorrectly choose A and 7, looking only for confirmation rather than counterexamples
" Is this selection task to psychology of reasoning what the microscope has been to biology? Or is it rather as the Rubik's Cube has been to biology? Just kind of baffling and fun. "

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