Orch-OR (orchestrated objective reduction)
Explanation
Roger Penrose, Oxford mathematician and physicist, together with Stuart Hameroff, anaesthesiologist from Arizona, have been developing since the 1990s one of the most radical theories of consciousness: Orch-OR (Orchestrated Objective Reduction). The thesis: consciousness arises from quantum processes in microtubules, structures of the neuronal cytoskeleton, through events of objective reduction of quantum superpositions.
Penrose came to the theory from Gödel's theorem and the impossibility (in his view) that human intelligence is computational. In The Emperor's New Mind (1989) and Shadows of the Mind (1994) he argued that certain mental processes (genuine mathematical understanding) require non-algorithmic capacities, which only a non-computable physics can provide. He sought such physics in a hypothetical new quantum mechanics.
Hameroff, who had been arguing for years that microtubules were candidates for quantum processing (because of their structure and because anaesthetics seemed to act on them), provided the biological substrate. Microtubules are protein tubes of the neuronal cytoskeleton with a crystalline structure; they could sustain quantum superpositions for tens of milliseconds before collapsing.
Each collapse (objective reduction, OR) would be an elementary moment of consciousness. The orchestration refers to the fact that collapses in microtubules of millions of neurons would be coordinated by classical synaptic processes, generating unified experiences. A conscious experience would be a sequence of OR events orchestrated at ~40 Hz (compatible with gamma oscillations).
The theory is highly controversial. Physically, the decoherence problem (quantum effects should not survive in the warm and wet brain) has been objected by Max Tegmark and others. Hameroff and Penrose have responded by proposing biological mechanisms protecting coherence. Recent studies have shown quantum effects in biology (photosynthesis, bird navigation) that lend some plausibility to the proposal.
Orch-OR is one of the few theories that offers a specific physical proposal addressing the hard problem (qualia would arise from specific OR events). Its critics consider it speculative to the extreme; its defenders believe it captures something important. Whether right or wrong, it is one of the most original and ambitious theories of recent decades, and raises deep questions about the relation between fundamental physics and mind.
Strengths
- A unique proposal on the non-computability of consciousness.
- Specific, potentially testable physical mechanism.
- Integrates quantum gravity and biology.
- Challenges standard physicalist assumptions.
Main critiques
- Quantum decoherence in a room-temperature brain is considered extremely fast.
- Penrose's objective reduction theory is speculative.
- Critiques from Tegmark and others on biological viability.
- Insufficient experimental evidence.