The idea that human consciousness might arise from odd quantum phenomena has intrigued scientists, philosophers, and science fiction writers, inspiring debate about whether the “hard problem” of consciousness could be explained by quantum effects.
A sweeping new review published in Frontiers in Psychology takes a hard look at the field and concludes that though quantum theories of consciousness are becoming more experimentally grounded, none have cleared the enormous scientific obstacles required to explain subjective experience.
The paper, authored by Xun Ma and Aoping Wang of Xiamen University in China, evaluates some of the most prominent quantum consciousness theories using three key lenses: whether the proposed quantum effects can physically exist in the brain, whether they actually explain conscious experience philosophically, and whether they can be experimentally tested against conventional neuroscience models.
The researchers argue that many discussions related to “quantum consciousness” rely more on emotional rhetoric than on measurable science.
“Quantum-theoretical terms are often invoked in a largely narrative or analogical manner without specifying their precise physical meaning or empirical applicability,” researchers write. “This practice often lacks rigorous argumentation, remains insufficiently constrained by clear mechanisms or empirical support, and therefore does not yet provide a substantive solution to the problem of consciousness.”
In the past few years, interest in the idea of quantum biology has steadily increased. Scientists have already demonstrated that quantum effects can play functional roles in biological systems such as photosynthesis and bird navigation. But the leap from quantum chemistry to human awareness remains enormous.
Central to the debate is consciousness itself, which remains one of science’s most enduring and elusive mysteries.
Neuroscience has become increasingly successful at explaining how the brain processes information, stores memories, and controls behavior — what philosopher David Chalmers famously labeled the “easy problems” of consciousness.
The harder question is why physical processes in the brain produce subjective experience at all. Why does seeing red feel like something? Why is there an inner experience accompanying thought?
Quantum theories try to bridge that explanatory gap by proposing that classical neuroscience alone may be insufficient.
In their review, Ma and Wang focus on three major “families” of theories currently attracting scientific attention.
The first and most famous is the Orch OR theory, developed by physicist Roger Penrose and anesthesiologist Stuart Hameroff. This model proposes that quantum computations occur within microscopic structures within neurons called microtubules. According to the theory, coordinated quantum collapses inside these structures generate moments of conscious awareness.
The idea has long been controversial because the brain is warm, wet, and noisy, conditions generally considered hostile to fragile quantum states. Physicist Max Tegmark famously argued in 2000 that quantum coherence inside neurons would collapse far too quickly to matter for cognition.
However, researchers note that more recent laboratory experiments have produced intriguing results. Some studies have identified unusual quantum-optical behaviors in microtubules, including coherent oscillations and energy-transfer effects that persist longer than previously expected. Other experiments suggest anesthetic drugs may interfere with these microtubule dynamics, possibly supporting Orch OR’s claim that consciousness depends on quantum processes.
Still, researchers emphasize that nearly all of this evidence comes from simplified laboratory systems rather than living human brains.
“Current expositions of Orch OR tend to remain at the level of an intuition: if there are quantum processes, novel conscious states may arise, without stating a clear rule of derivation from quantum-state dynamics to the what-it-is-likeness of experience,” researchers write.
In other words, even if quantum effects exist inside neurons, scientists still have no explanation for why those effects should generate subjective awareness.
The second major theory examined in the review concerns nuclear spins and hypothetical structures known as Posner molecules. Proposed by physicist Matthew Fisher, the theory suggests that phosphorus atoms inside the brain may preserve quantum phase coherence long enough to influence neural processing.
Unlike electron-based quantum systems, nuclear spins are relatively immune to environmental noise, making them potentially more stable in biological tissue. The theory predicts that subtle differences between isotopes, atoms with different nuclear characteristics, could shape brain function or even consciousness itself.
Some experiments involving lithium and xenon isotopes have hinted at unusual spin-related biological effects. However, researchers stress that evidence remains sparse and heavily disputed.
Scientists have yet to directly observe long-lived quantum entanglement in Posner molecules inside living brains. Therefore, competing explanations rooted in conventional chemistry also remain plausible.
Ma and Wang describe the nuclear-spin hypothesis as scientifically intriguing but philosophically incomplete. Even if quantum spins influence neural activity, that alone would not explain why consciousness exists.
The third family of theories involves reports of large-scale “non-classical” signals detected using MRI scans. In 2022, research led by physicist Dirk Kerskens reported heartbeat-linked quantum-like signals in the brains of conscious participants. The findings generated immediate attention because they indicated the presence of macroscopic quantum effects across the entire brain.
However, critics quickly challenged the work, arguing that the observed signals could simply reflect conventional physiological artifacts associated with heartbeat and blood flow.
The new review notes that the controversy remains unresolved. Independent replications have not yet confirmed the findings, and the debate has become a case study in the difficulty of separating genuine quantum signals from ordinary biological noise.
Nevertheless, Ma and Wang maintain that these theories of quantum consciousness deserve serious scientific testing rather than outright dismissal.
Importantly, researchers praise the growing shift toward experimentally verifiable predictions. Unlike earlier eras of quantum consciousness speculation, modern researchers are increasingly proposing measurable hypotheses involving anesthesia, isotope substitutions, fluorescence signals, and cutting-edge imaging techniques.
That transition from abstract philosophy to laboratory science may represent the field’s biggest advance.
Researchers call for stricter scientific standards moving forward, including pre-registered studies, open data sharing, multi-center collaborations, and publication of null results. Because quantum consciousness claims are so extraordinary, they argue, the burden of proof must remain exceptionally high.
In their paper, Ma and Wang also repeatedly return to one key distinction: discovering quantum influences in the brain would not automatically solve the problem of consciousness itself.
Even if future experiments verify that neurons create quantum consciousness in some capacity, the central mystery of subjective experience could remain untouched.
“Quantum mechanisms, therefore, look, at the current stage, more like potential realizers of consciousness than like complete theories of consciousness,” researchers conclude.
That finding may frustrate anyone hoping for a definitive answer to the question of quantum consciousness. Yet, researchers propose that while no definitive answer exists, the field is slowly maturing from speculative theory into a more stringent scientific enterprise.
For now, the authors argue that caution and curiosity must coexist.
“In the explorations ahead, progress should be guided by the scientific method, advancing with a balance of curiosity and skepticism,” researchers write. “The riddle of consciousness remains profoundly complex: Quantum mechanics may be one piece of the puzzle, but a solution will likely require sustained multidisciplinary collaboration.”
Tim McMillan is a retired law enforcement executive, investigative reporter and co-founder of The Debrief. His writing typically focuses on defense, national security, the Intelligence Community and topics related to psychology. You can follow Tim on Twitter: @LtTimMcMillan. Tim can be reached by email: tim@thedebrief.org or through encrypted email: LtTimMcMillan@protonmail.com