Shaking the snow globe

Shaking the snow globe is Robin Carhart-Harris’s metaphor for a proposed therapeutic action of psychedelics: temporarily disturbing rigid patterns of thought so that more flexible, potentially healthier patterns can take shape. It links changes observed in the brain with the felt experience of being mentally stuck, but remains an explanatory model rather than a literal description of what happens in the brain.

The Metaphor's Mechanism

Carhart-Harris uses the snow globe to make a counterintuitive claim: a temporary increase in mental disorder may be useful when the mind has become excessively fixed. A high-dose psychedelic experience can disrupt destructive patterns of thought and open a period of flexibility, or entropy. As the snow settles, more salubrious patterns and narratives may coalesce. The image gives this process a sequence: disturbance loosens the existing arrangement; the unsettled interval permits alternatives; and settling allows a different arrangement to form.

A related account from Mendel Kaelen, a postdoctoral researcher in the Imperial College London lab, gives the metaphor a more specific shape. He compares the brain to a snow-covered hill and thoughts to sleds. Repeated trips down the hill carve a small number of main trails, making later thoughts more likely to follow those familiar routes. Many of these well-traveled neural connections pass through the Default mode network. In the metaphor, repetition is not neutral: the established path draws the next thought toward itself, while other directions become harder to take.

Psychedelics, in Kaelen’s extension, temporarily flatten the snow. The familiar trails disappear, and the sled can travel in other directions, exploring new landscapes and making new pathways. The metaphor therefore describes not simply a pause in habitual thought but a moment when the mind may be more impressionable. A song, an intention, or a therapist’s suggestion can provide a nudge that influences the course taken once the snow begins to settle.

Rigidity and Therapeutic Change

The model is offered as a way of understanding why some disorders might respond to a temporary disruption of habitual mental activity. Carhart-Harris places depression, anxiety, obsession, and the cravings of addiction toward the excessively ordered end of a spectrum. In this account, suffering can involve pathways so fixed that thought repeatedly returns to the same destructive patterns. Psychosis, by contrast, lies toward the excessive-entropy end of the spectrum, which may help explain why psychedelic therapy probably does not work for it. The snow-globe metaphor is thus not a claim that more disruption is always better: its proposed value depends on the mind’s starting condition.

The metaphor also connects to Matthew Johnson’s idea of a mental reboot, described as a biological control-alt-delete key. A reboot jolts the brain out of destructive patterns and gives new ones an opportunity to take root. Carhart-Harris’s image specifies what that opportunity might involve: the old trails are disturbed, and a more flexible interval opens before new routes become established. Franz Vollenweider’s neuroplasticity hypothesis offers another version of the same possibility, suggesting that psychedelics may make patterns of thought and behavior easier to change. These are related proposals, not interchangeable proof of a single mechanism.

Carhart-Harris also compares the process to annealing in metallurgy. Energy is introduced into a system so that it can bend and change rather than remain fixed in its previous form. Researchers at Johns Hopkins University use a similar image in describing psychedelic therapy as an interval of maximum plasticity, during which proper guidance may help people learn new patterns of thought and behavior. Together, the metaphors emphasize that disruption alone is not the proposed treatment: what happens during the period of increased flexibility, including the guidance available, matters to the possibility of change.

Evidence and Uncertainty

The account distinguishes these explanatory images from the brain itself. Neuroimaging at Imperial College London has identified measurable changes in activity and connectivity during psychedelic experiences, and similar findings have been replicated in other laboratories using psilocybin, LSD, and ayahuasca. In particular, changes involving the Default mode network offer a possible way to connect experiences such as rumination and rigid self-focused thought with observable, potentially alterable brain activity. That evidence lends credence to the metaphors, but it does not establish that snow is literally being flattened or that the imagery fully explains therapeutic effects.

The durability of any change remains unsettled. It is not yet clear whether newly available connections persist after a psychedelic has worn off or whether the brain returns to its previous organization. Recalling an experience, reinforcing it through integration, or using meditation to reenact an altered state could, in principle, exercise new circuits and help them endure. Vollenweider’s proposal that psychedelics open a window for neuroplasticity is consistent with this possibility, but the account stresses that it remains speculative and that little research has mapped the brain before and after an experience to determine what changes last.

Entropy's Double Meaning

The metaphor’s force depends on reversing the ordinary negative association of entropy. Entropy commonly suggests deterioration and the gradual undoing of hard-won order. Carhart-Harris’s account instead treats some increase in entropy as potentially beneficial when excessive order has become rigidity. The snow globe makes that reversal legible: disturbance can be destructive in one context, yet create room for change in another.

That reversal also leaves a question open. If some entropy is a positive quality of mental life, perhaps aging involves not only disorder but a decline in the mind’s capacity for flexibility. This is raised as a possibility, not established as a scientific conclusion. The metaphor’s lasting contribution is its conditional account of change: disrupting entrenched routes may create an opening, but the new paths, their guidance, and their persistence remain matters to be demonstrated.