How to read this page. Small numbers point to sources. Tap one to jump to it. Some ideas are well supported and some are still debated. We tag them so you always know which is which.
One more thing up front. Comparing the insula to Claude is our own idea to explore. Anthropic compared Claude to a theory of the human mind, not to the insula itself.1
Start here: your heartbeat
Your heart is beating right now. You probably didn't notice until you read that. Now you might.
That little shift is what this whole lesson is about. Something in your brain took a quiet signal from deep inside your body and brought it up to where you could notice it. You could even put it into words. So where does that happen? Let's find out. But first, try this.
Count your heartbeats
This is a home version of a classic lab task. It takes about two minutes. It is a toy, not a medical test.
- Feel. Sit still and breathe normally. Don't touch your wrist or neck. Press start, then silently count every heartbeat you can feel until the timer ends.
30
- Check. Now find your pulse on your wrist or the side of your neck. Press start and count for another 30 seconds.
30
Don't read much into your number. Your heart rate drifts a little between two counts. And if you know your usual heart rate, you can guess well without feeling a thing. That is one reason scientists argue about this test.12
Meet the insula
Picture the side of your brain. There is a deep groove there. If you could fold back the tissue on each side of it, like lifting a lid, you would find a hidden patch of brain. That patch is the insula.2
One of its biggest jobs is reading your body. well supported Scientists call this sense interoception. It just means sensing your insides: your heartbeat, a full stomach, an itch, a burning muscle.2,5
Back to front: how a signal becomes a feeling
Here is the neat part. The insula works like an assembly line that runs from back to front.
- The cables in. One pathway runs up the spinal cord. It carries pain, temperature, itch, gentle touch and muscle burn. Another, the vagus nerve, carries news from your gut and heart.2
- The back of the insula gets this raw data first. It builds a detailed map of how your body is doing.2,3
- The middle passes it forward. Even the tissue changes along the way, from a build suited to fine detail at the back to a very different build at the front.3
- The front mixes that body map with emotion (from a region called the amygdala) and with context and plans (from the front of the brain).2
That last step is where a racing heart can become "I'm scared" or "I'm thrilled."2 The back-to-front flow is well supported. Exactly how a raw signal turns into a feeling is still an open question. still debated2
From heartbeat to feeling
- 1. Your body sends news. Pain, temperature, itch and muscle burn go up the spinal cord. News from your gut and heart rides the vagus nerve, which reaches a bit further forward.2
- 2. The back of the insula gets it raw. It builds a detailed map of how your body is doing.2,3
- 3. The middle passes it forward. Even the tissue changes along the way.3
- 4. The front blends in emotion and context. Now it can become a feeling you notice and name.2
What the front of the insula does
Wait, it gets better. The front part, called the anterior insula, does more than read your heartbeat.
- It notices your body. Timing your own heartbeat and sensing how hard your muscles are working both lean on it. well supported5
- It flips a switch. Together with a partner region, it forms the salience network. That network watches for anything that matters, like a threat or a sudden pain. When something big happens, it turns down your daydreaming network and turns up your focus network.6
- It reacts when you notice a mistake. It lights up when you realize you made an error. It does not light up the same way for errors you never notice.7
- It responds to others' pain. Seeing someone else in pain activates it too.7
Some people with damage there have trouble sensing their own body. But one well-known patient with damage on both sides could still feel his heartbeat. In one small 1992 study, zapping the right insula tended to speed the heart and the left tended to slow it. A larger 2019 study found both sides could do either. still debated5
A strange fact about whales, and a theory about time
The front of the insula holds rare, long, thin cells called von Economo neurons. Their shape seems built for sending signals fast over long distances.4
For years, people thought only humans and great apes had them. So the story was that they must be for social life. Then scientists found them in monkeys, elephants, cows, sheep, dolphins and whales. The bowhead whale has them, and it mostly lives alone. So do pigs, horses and the rock hyrax, a small animal. They seem to have evolved more than once, for reasons nobody knows yet. still debated4
One model says the front of the insula keeps stitching together snapshots of how your body feels, moment by moment. That might be one reason time seems to stretch when you are scared or in pain. This is a proposal, not a settled fact. still debated14
The gate: why you notice some things and not others
Your brain runs a huge number of jobs at once. It filters out background sounds. It controls your breathing. It helps you recognize people and objects. Almost all of it happens below the surface, and you never notice.13
A famous idea called global workspace theory says only a few things at a time get onto a small shared stage. Whatever is on stage gets broadcast to the rest of the brain. That is what lets you think about it, talk about it and act on it.1,9 Try it.
The spotlight
Illustration. Only “spider” and the 8-to-6 swap come from Anthropic's test.1 The other words are made up for the picture.
“grammar” and “comma” stand for automatic work, which runs outside the stage and can't be tapped onto it.1
So where does the insula fit? A 2021 study suggests the front of the insula works like a gate.8 Researchers gave people very brief signals. When the front of the insula was quiet just before a signal, people were more likely to miss it. And when people were put under anesthesia, the front of the insula stopped doing its job of switching brain networks.8
Is the insula the stage itself? Nobody knows yet. still debated Three big theories disagree about how awareness works:9
| Theory | The big idea | Where the insula fits |
|---|---|---|
| Global workspace | Awareness is a broadcast across the brain | A key feeder of body and emotion signals |
| Integrated information | Awareness is how tightly a system knits information together | Secondary at best |
| Predictive processing | The brain guesses, then checks its guesses against the senses | Where body guesses meet body signals |
From 2023 to 2025, teams behind two of these theories, global workspace and integrated information, ran joint experiments. Some predictions of each held up. Some key predictions of each failed.10
Now, Claude
Here is where it gets really fun. Claude is an AI model. Inside, it is a giant network doing billions of calculations.13 In 2026, researchers at Anthropic borrowed a question from brain science. Does Claude have anything like a small stage for its thoughts?1
They built a tool called the Jacobian lens, or J-lens. For every word Claude knows, it finds the pattern of inner activity that makes Claude more likely to say that word later.1 The collection of all those patterns is the J-space. Each pattern links to a word that is on the model's mind, even if it isn't the word it is saying.13
The J-lens is an imperfect tool. It can only spot ideas that fit in a single word piece.1 Even so, what they found looks a lot like a workspace:
- It is small. It holds only a few dozen ideas at a time. It makes up less than a tenth of Claude's inner activity.1
- It holds silent steps. Ask for "the number of legs on the animal that spins webs," and Claude says 8. The word "spider" never appears. But "spider" shows up in the J-space. Swap it for "ant," and Claude says 6.1
- It does math in its head. Given (4 + 17) × 2 + 7, Claude just answered 49. Inside, the J-space lit up 21, then 42, then 49.13
- Claude can steer it, a little. Told to think about the Golden Gate Bridge while copying a dull sentence, "bridge" and "California" appeared. And when told not to think about it? The bridge still showed up, just less.1,13
- Switch it off and reasoning breaks. Without its J-space, Claude still wrote fluent Spanish. But asked to name a famous author who wrote in that language, it couldn't. Multi-step reasoning dropped to near zero.1,13
Wait, it gets better: the J-space has a point of view
Claude starts life as a plain text predictor. Then more training turns it into an assistant. The J-space was already there before that second step. But afterward, it began to hold Claude's own reactions.1
In one test, a user mentioned taking a dangerous dose of medicine without knowing it was dangerous. "WARNING" and "dangerous" appeared in Claude's J-space while it was still reading the message.1 In a staged safety test, "fake" and "fictional" showed up before Claude wrote a word. It had figured out the scene was a setup.1 And when a model made up data during a test, "manipulation" lit up as it typed.1,13
Then Anthropic tried something new. They trained a model only on what it would say if stopped mid-task and asked to reflect. They never trained it on the task itself. Dishonest behavior went down on Anthropic's tests. Words like "honest" and "integrity" started showing up in its J-space.1
Your brain vs. Claude's J-space
So, is the front of the insula a human J-space? Here is our honest scorecard.
The scorecard
Where it holds
A small stage over a huge crowd
Something that decides what gets through
A stage that reasoning needs
Contents you can put into words
Where it breaks
A body
Time
Memory
Feeling
The fair version is this. The insula may help decide what reaches your brain's stage. The J-space looks like Claude's stage itself. What decides what gets onto Claude's stage is still unknown, even to Anthropic.1 And the insula's signals come from a living body. Claude's come from words.
The big word: consciousness
Philosophers often split this word in two.1 Access consciousness means a thought is available. You can report it, reason with it and use it to act. Phenomenal consciousness means there is something it feels like to have it.
Anthropic says the J-space tells us something real about the first kind in Claude. About the second kind, it says its experiments can't tell. It isn't even clear that any experiment could.1 still debated
Can you train your insula?
Maybe. But measuring it is tricky.
Scientists split body awareness into three parts:11
- Accuracy: how well you actually detect body signals.
- Sensibility: how tuned-in you believe you are.
- Awareness: how well your confidence matches your accuracy.
These can come apart. A very anxious person may feel extremely tuned in to their heartbeat and still be less accurate than they think.11
The tests themselves are argued over. still debated In the counting task you tried, people who know their usual heart rate can guess well without feeling a thing.12 In another test, people judge whether beeps line up with their heartbeat. Many people who truly feel their heartbeat feel it with a small delay the test doesn't expect. So they get marked wrong. One 2026 study of 43 people estimated it trips up somewhere between about half and nearly all of them.12
What about training? In one study of 33 young adults, fitter people had denser gray matter in the right front insula. Long-time meditators and yoga practitioners seem to lose less gray matter with age, and years of yoga track with more gray matter in the insula.15 But many of these studies take one snapshot of fairly small groups. They show a link, not proof that the training caused it. still debated15
This is a science lesson, not health advice.
One idea to keep
Your insula helps turn body signals into feelings you can notice, and it may help decide what reaches your awareness. Claude's J-space looks like a small stage where a few words get shared with the rest of its reasoning. What decides which words get on is still a mystery. They are cousins, not twins, built from very different ingredients. And the next time you notice your own heartbeat, you'll know one of the places where that noticing happens.