Science Fictions Episode 97: The 2D:4D digit ratio
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Mar 10, 2026 They examine the 2D:4D digit ratio and the long history of research and hype around it. They cover claims linking finger length to aggression, trading success, musical ability, sexuality, penis size, and COVID outcomes. Measurement problems, replication failures, statistical pitfalls and dubious causal chains get called out. The tone is skeptical and often humorous.
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The Trader Study That Never Replicated
- A 2009 PNAS study claimed a large correlation (r≈0.48) between right-hand 2D:4D and earnings of City of London traders.
- Stuart highlights it used only 44 traders and has not been convincingly replicated in larger studies.
Orchestra Study With Implausible Uniform Result
- A 2000 paper claimed all 70 orchestral musicians were shifted toward masculinized right-hand 2D:4D versus 164 controls.
- Tom and Stuart find the result implausible and note subsequent studies gave contradictory or null outcomes.
Chained Hypotheses Make Tiny Detectable Effects
- Many seemingly interesting chains (e.g., husband's 2D:4D → male behavior → wife's ring-wearing) multiply small effects and become vanishingly small.
- Stuart demonstrates such chained hypotheses need very large samples to detect reliably.