High-entropy brain state

High-entropy brain state is the more uncertain, less tightly organized mode of cognition described by Robin Carhart-Harris in his theory of conscious states. It gives a scientific account of why psychedelic experience can loosen habitual thought and multiply possible perceptions and ideas, while also making clear that increased mental freedom is not automatically insight, healing, or lasting change.

The brain’s order and its costs

The model begins with the brain’s work of reducing uncertainty. In adulthood, predictive coding helps it test reality, make reliable predictions, and use mental and physical energy in ways that support survival. This orderly operation is valuable: it encourages foresight, reflection, and resistance to wishful or paranoid beliefs. But Carhart-Harris’s 2014 paper, “The Entropic Brain: A Theory of Conscious States Informed by Neuroimaging Research with Psychedelic Drugs,” argues that order has a cost as well as a benefit. The structures that make cognition more reliable can also narrow consciousness and constrain what the mind is able to think.

Carhart-Harris distinguishes this adult, reality-oriented mode from primary consciousness, which he associates with an earlier and more emotionally influenced form of cognition. In his account, the emergence of the Default mode network accompanies a coherent sense of self and supports self-reflection and reason: magical thinking gives way to secondary consciousness, which works to represent the world precisely and reduce surprise. High entropy describes movement away from this tightly regulated mode, not simply a malfunction or a state of disorder without structure.

A spectrum of mental states

Carhart-Harris presents mental states along a spectrum from high to low entropy. At the high-entropy end he places psychedelic states, infant consciousness, early psychosis, magical thinking, and divergent or creative thinking. The opposite end includes narrow or rigid thought, addiction, obsessive-compulsive disorder, depression, anesthesia, and coma. The range is deliberately striking: states usually treated as opposites, such as psychedelic experience and early psychosis, can share a position on the same dimension without becoming equivalent in meaning or consequence.

The model also reverses a familiar assumption about psychological disorder. Some entrenched conditions may reflect not too little order but too much. When self-reflective patterns become rigid, the self can dominate attention; in depression, an overactive Default mode network may sustain repetitive rumination until the person’s attention is increasingly closed off from the surrounding world. Carhart-Harris therefore proposes that disrupting fixed patterns could matter for depression, addiction, obsessions, and eating disorders. This is a proposed therapeutic rationale, not proof that increasing entropy by itself treats these conditions.

What changes under psilocybin

Carhart-Harris describes Psychedelic compounds as temporarily quieting the Default mode network and loosening the ego’s control over cognition. His explanation is not merely that one regulating system falls silent: he argues that an older mode of consciousness re-emerges, allowing unconscious material to enter awareness. The resulting increase in entropy makes the mind less constrained, but does not guarantee that its contents will be coherent or useful.

Brain-imaging work at Imperial College London gives the model a network-level counterpart. In the team’s account, specialized systems, including the Default mode network and visual-processing networks, become less distinct, while communication across the brain increases. A 2014 study using magnetoencephalography compared ordinary waking consciousness with the brain after an injection of Psilocybin. Under the drug, thousands of connections formed between distant regions that usually exchange relatively little information. Rather than sending most traffic along a few heavily used routes, the brain appeared to distribute it across many more pathways. The researchers interpreted this as reduced specialization and greater global interconnectedness.

The proposed consequences range from confusing to potentially productive. If memory and emotion systems communicate more directly with visual processing, fears, wishes, and expectations may shape perception in ways associated with primary consciousness. New cross-system connections may also contribute to synesthesia, hallucination, creative insight, or fresh meanings attached to familiar things. Entropy thus enlarges the variety of available mental states: many may be bizarre or senseless, while some may prove imaginative or revelatory. The model explains how unusual experience becomes possible without treating every unusual perception as a discovery.

Possibility, creativity, and uncertainty

Carhart-Harris compares increased mental variation to variation in evolution. A wider range of possibilities gives the mind more material from which useful solutions might emerge; in this sense, entropy may help explain why psychedelic experiences are sometimes associated with thinking beyond established habits. The analogy concerns possibility rather than guaranteed progress: selection still matters, and a proliferation of mental states does not ensure that any particular idea is accurate or beneficial.

Whether the new neural connections persist after the drug wears off remains an open question. Findings from Roland Griffiths’s laboratory that psychedelic experience can be followed by long-term changes in openness suggest that learning may occur during a period of altered connectivity. Carhart-Harris also raises the possibility that recollection, integration, or meditation could exercise and reinforce pathways opened during the experience. Franz Vollenweider has proposed that this period may support neuroplasticity, making patterns of thought and behavior more changeable. Yet the book stresses that this remains speculative: there has been little before-and-after mapping to establish which changes endure. High-entropy brain state therefore names both a promising opening in cognition and a limit in current knowledge; the mind’s temporary expansion is observable in the model, but its lasting consequences are not settled.