Consciousness and Quantum State Reduction—Which Comes First?

Stuart Hameroff

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


Consciousness and reality are related through the “measurement problem” in quantum mechanics, i.e., why we do not consciously perceive particles as quantum superpositions of multiple possibilities, as they appear to be when unobserved, but rather perceive them consciously as being in definite states or locations. Quantum pioneers Niels Bohr, John von Neumann, Eugene Wigner, and Henry Stapp concluded that subjective conscious observation causes quantum state reduction (“subjective reduction” (SR)), that “consciousness collapses the wavefunction.” However, Sir Roger Penrose suggested instead that quantum state reduction occurs spontaneously due to an objective threshold property (“objective reduction” (OR)) in fundamental spacetime geometry, collapsing the wave function and causing moments of conscious experience (“collapse causes consciousness,” or “collapse is consciousness”). Penrose OR would be occurring ubiquitously and randomly in the environment (“decoherence”) resulting in ubiquitous proto-conscious moments. The Penrose–Hameroff “Orch OR” model of orchestrated objective reduction suggests that microtubules inside brain neurons “orchestrate” quantum computations which “halt” by Orch OR to produce moments of a full, rich conscious experience.

Original languageEnglish (US)
Pages (from-to)31-40
Number of pages10
JournalActivitas Nervosa Superior
Issue number1-2
StatePublished - Jun 15 2019


  • Anesthesia
  • Consciousness
  • Henry Stapp
  • Measurement problem
  • Microtubule
  • Objective reduction
  • Orch OR
  • Quantum computing
  • Quantum state reduction
  • Roger Penrose
  • Spacetime geometry
  • Subjective reduction
  • Superposition
  • Tubulin

ASJC Scopus subject areas

  • Neurology
  • Cognitive Neuroscience
  • Clinical Neurology
  • Psychiatry and Mental health
  • Biological Psychiatry
  • Behavioral Neuroscience


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