Class 7a: Why do we need theory?

Systems Biology

Andrés Aravena, PhD

November 16, 2023

Some people distrust Science

  • Anti-vaccine
  • Climate change denial
  • Flat Earthers
  • and several others

Can Science be trusted?

  • Are eggs good or bad food?
  • How much water should we drink?
  • How much salt?
  • Does fat make you fat?

PLOS Medicine 2005

Replicability crisis

  • In 2009, 2% of scientists admitted to falsifying studies at least once
    • 14% admitted to personally knowing someone who did
  • A 2016 poll of 1,500 scientists reported that 70% of them had failed to reproduce at least one other scientist’s experiment
    • 50% had failed to reproduce one of their own experiments

Science August 2015•vol 349 issue 62519


  • reproducibility of 100 studies in psychological science from three high-ranking psychology journals
  • 36% of the replications yielded significant findings
    • compared to 97% of the original studies
  • The mean effect size in the replications was approximately half the magnitude of the effects reported in the original studies

This is not limited to psychology

Why does this happens?

Journal of the Royal Statistical Society and American Statistical Association

Cargo cults

Original context

Richard Feynman

  • Physicist
  • Excellent professor
  • Worked in the Manhattan Project at 25 years old
  • Nobel Prize on Physics in 1965

Who do you want to be?