What Humans, Animals and Plants Tell Us About Consciousness | Michael Pollan

The episode opens with a deliberately unsettled position. After studying consciousness and surveying the theories of it, the speaker concludes that science does not yet understand how brain matter produces conscious experience, or even whether that is how consciousness arises at all.

we have no idea about consciousness really,

To show how wide the space of possibilities is, the speaker raises an alternative held by some doubters: the brain might channel consciousness rather than generate it. In this analogy consciousness is like electromagnetic waves and brains are like radio or TV receivers. Just as you would not search inside a television for the woman delivering the weather report, you might not find consciousness by looking inside the brain.

The speaker is careful about the limits of this claim. They do not say the receiver model is true, only that they no longer dismiss it. The reason given is that the default assumption has not earned much confidence:

our presumption that consciousness is an emergent property of brain complexity, that idea doesn't have much traction.

Andrew Huberman introduces himself as a professor of neurobiology and ophthalmology at Stanford School of Medicine. He introduces his guest, Michael Pollan, as the author of How to Change Your Mind (on psychedelics), The Botany of Desire (on how humans and plants co-evolved and collaborated to thrive), The Omnivore's Dilemma (on food and nutrition), and most recently A World Appears, A Journey into Consciousness.

Huberman says the discussion centers on consciousness and brings together science and philosophy. He also says it goes deep into the ego, meaning our sense of self, which he describes as both important to and limiting of our understanding of ourselves and of life. He stresses that the conversation is less abstract than this summary suggests, and that it covers plant or psychedelic medicine and ways to gain new perspective on oneself, others and the planet.

Huberman notes that the podcast is separate from his teaching and research roles at Stanford, and that this episode includes sponsors.

Before turning to consciousness, the conversation goes to Wendell Berry, described as a poet, farmer and essayist. Both participants say they are fans. One of them reports that Berry had died roughly two weeks earlier and believes he was 92.

One speaker recalls knowing Berry personally. They interviewed him on stage several times, were interviewed by him in Lexington, Kentucky about one of their books, and visited his house and the long-legged house on the river where he writes. Berry, they say, kept trying to persuade visitors of the beauty of tobacco culture while setting aside the cigarette and lung cancer side of it. He valued it as the one time the whole community gathered and racial lines were crossed, and he admired the tobacco barns with their drying slots.

The more substantive point concerns the ethics of acting in nature. While writing a first book, Second Nature, the speaker treated the garden as a small-scale version of how humans should behave in nature, because gardening brought pests, problems and fertility issues. The American tradition descending from Thoreau, John Muir and Emerson celebrates wilderness and casts people as spectators, which a gardener cannot afford to be. The speaker calls Thoreau's suggestion that weeds have as much right to the garden as the bean plant "crazy".

In this account, Berry's essays offered a way out. Humans have a legitimate quarrel with nature, must change it to survive, and are by nature the species that remakes its surroundings. The speaker says this reframing clarified their whole view of environmentalism.

But it has to be done sort of more like a marriage than a domination.

One speaker says neuroscientists are trained to avoid consciousness. They describe it as a career risk that only researchers already established in a specific field, such as memory or neuromuscular junctions, felt free to discuss once they had prizes and stature. They suggest that part of the difficulty is that consciousness is hard to define, and they ask whether it can be stated in a sentence or given an operational definition.

The answer begins with a paradox. Consciousness is the one thing we can be sure of, and everything else is known through it and is therefore an inference. Even so, it resists definition.

there is nothing we know with more certainty than the fact that we're conscious.

Two working definitions are offered. The first is "subjective experience", which a toaster lacks. The speaker adds, and leaves for later, the view that AIs also lack it. The second comes from the philosopher Thomas Nagel's 1970s essay What Is It Like to Be a Bat?: if being something is like anything, it is conscious. We cannot know exactly what bat experience is like, but we can imagine navigating by sonar instead of light, so bats count as conscious. The speaker says the open question of whether it is like something to be a computer is one "we're going to have to face", and that Nagel's test is the definition they use.

Human consciousness, the speaker says, adds further layers to this baseline. These include awareness of being aware, self-reflection or metacognition, and emotion. The result is a highly elaborated form compared with that of some other creatures.

The book draws a distinction, which the speaker says some scientists also make, between sentience and consciousness. Sentience is the more basic ground floor. It includes awareness of one's environment and recognition of whether changes in it are good or bad.

The claims about how widespread sentience is are hedged. It "may be universal" and "may be a property of life", and one "can make a case" that plants and single-celled organisms have it. The proposed function is survival in a constantly changing environment, where an organism cannot have everything it needs to know programmed in by instinct.

In this framework, consciousness is the human way of being sentient. Each creature has its own version, shaped by its body type, its sensorium and the scale of time and space it lives at. The speaker argues that treating the human version as the standard for every creature "seems kind of crazy."

The conversation then tests this framework. If responding to the environment is a key part of consciousness, plants, barnacles and bacteria all qualify. One participant adds that bacteria can sense light, can tell morning from evening, and have chemotaxis, which lets them tell food from something toxic.

The counterpoint asks whether these organisms know that they know. The questioner says they are inclined to draw the line at awareness of one's own response. A plant may furl and unfurl in light, but does it know it is responding, and why? The questioner grants that humans often respond without knowing why. Still, sipping tea that is too hot comes with some sense of what one will do next and why, whereas the other cases seem merely reflexive.

The reply accepts that such responses are reflexive but disputes that they are always programmed. It argues that even plants meet novel situations calling for an intelligent response that is not necessarily encoded in their genes. The disagreement is left open here. One side places the threshold at self-aware response, the other at flexible, unprogrammed response.

To support the claim of non-programmed responses, the speaker describes findings from the field of plant intelligence, which they say they explored in depth.

Maze navigation: a corn plant placed in a maze with fertilizer (ammonium nitrate) in one corner sends its roots along the fastest path to it. This is a situation the plant does not really face in nature, and the speaker presents it as problem-solving ability. Sound and defense: when plants hear a recording of caterpillars chewing leaves, they respond by sending toxins or bad-tasting chemicals to the leaf. Sound and water: plants respond to the sound of water and will grow down toward water heard running through a pipe. Senses: plants are described as having "like 20 senses" compared with humans' "five or six", including gravity, which humans cannot sense, as well as pH and whether nutrient levels lie on a positive or negative gradient.

The speaker calls the response to anesthetics one of the most curious findings: plants respond to the same anesthetics humans do. They anticipate the objection that plants are already "out" and answer that plants do have behaviors, which are simply very slow. The excerpt ends as the speaker starts to describe an experiment with a fast-moving plant, a Venus flytrap placed in a bell jar. The result is not included in this section.

Several limits apply to this section. The plant findings are described from memory, with no studies, authors or magnitudes cited. The figure of about 20 plant senses is approximate. The anesthetic experiment is cut off before any outcome is reported. These examples are offered as evidence of intelligent, flexible behavior, and the section does not establish whether such behavior involves awareness, which is the question the questioner raised.

This part of the conversation starts in the middle of an example. Plants exposed to an anesthetic gas such as xenon, or "anything you can put in gas form," stop responding to an insect crossing their threshold, where normally they "would clamp down." The speaker treats this as a real puzzle: "What exactly are they losing when they are under?"

The speaker is careful with terms. Calling the lost capacity consciousness is "a long way to go." The speaker says they don't use the word consciousness for plants, while noting that they met scientists who do. Their preferred description is "a loss of sentience" during anesthesia.

Anesthesia is an imperfect reference point for this question. The speaker notes that "We don't even know how they work on us," and points out that xenon is an inert gas that still "puts you out." The exchange adds a reassurance for anyone facing surgery: anesthesiologists "have gotten much better" and "know what they're doing." The open question is how anesthetics work, not whether they are used competently.

The conversation then breaks for sponsor messages from 8Sleep and Rora before returning to the main discussion.

When the discussion resumes, self versus other is proposed as "one potential window" into consciousness. The starting observation is that most people "know that they are them and they know what's not them." The suggested analogy comes from development: growing nerve cells "know the difference between them and other cells," so this distinction is "already set up" at the cellular level.

The neuron analogy is tied to an earlier example of a root growing toward fertilizer. The idea is that nerve cells can follow a simple rule: grow as far as possible, connect with as many other nerve cells as possible, and know the difference between self and other. Someone adds that this holds "Even within the same species." Exceptions are acknowledged, along with the caveat that "it's not straightforward to build a brain." Still, the claim is that "you don't need a ton of signals": you need signals for where growth is allowed and where it is not, which are called chemoattractants and chemorepellants.

Dendrites and axons get the same treatment. Their "beautiful architectures" are described as products of "a simple rule of self-avoidance": branches recognize that they belong to the same neuron and branch again whenever they come too close to one of their own. The final shape also depends on what surrounding cells are doing, and this is said to help produce different cell types, with "other features to it too."

so simple rules can build immense complexity that's that's the point

The speakers find a parallel in tree roots. Combining self-recognition with a rule to "get as much stuff as you can" sounds selfish, but it is described as producing "a tiled system" because every unit follows the same rule. As a result, "No tree, no neuron gets too much space."

There is a clear caution about how far this goes. The branching of cells is "not, you know, thinking." The leap to whole organisms is put forward tentatively: a person knows the difference between themselves and another person or a microphone, and plants seem to tell themselves apart from fertilizer. Being clear about "what's me and what's not me" is offered as possibly the most important rule that "perhaps builds up to the consciousness thing," and the hedge is repeated: "It's just perhaps."

Two plant examples support the self-other rule. Related plants with "some genetic connections" will share soil and grow together. Unrelated plants compete, "even if they're the same species." Likewise, a plant shaded by another plant grows fast to get above it, but a plant shaded by itself does not, as if registering that "we're getting the light over there."

The idea that simple rules can build very complex creatures is fully accepted. How that leads to consciousness is left open. Self and other is called "an important part of consciousness," but a qualification follows: the self is described as "the most elaborate or advanced manifestation of consciousness," and "you can have consciousness without a self."

Three sources of evidence are offered for selfless consciousness: meditators "know this," psychedelics can provide such an experience, and ordinary waking may as well. The speaker describes a roughly 500-millisecond window after waking when a person is "reconstituting" who and where they are. They add that it is 750 milliseconds in a hotel room, something they noticed that morning. These figures come from personal experience, not a cited measurement.

The speaker calls it "kind of weird" that there is a consciousness "not organized around a self." They note that Buddhists have known this "for a long time" but still call it "a strange idea."

The conversation turns to the plant medicine community. The questioner says they have spent "Not a lot" of time with this community and are not "a heavy psychonaut." Even so, they say that people who spend time in the jungle and with plant medicines have a real understanding that is not "just conjecture." In support, they note that pharmacists say most drugs were bioprospected from the jungle, and that big pharma isolates and synthesizes compounds from jungle plants and other plants.