A toddler at the breakfast table points at a cup and says “more milk.” Most children can put two words together like this by their second birthday, after hearing roughly nine million words.1,2 Nobody gave the toddler the internet to read.
A chatbot such as ChatGPT, Claude or Gemini runs on an AI model, and the model reads trillions of words before it can hold a conversation. Researchers call this the question of sample efficiency: how much a learner gets out of each example. On that measure the toddler wins by a mile.
The short answer is that the two learn in different ways, at different times. A child starts with a brain that evolution shaped for learning, and she learns from a world she can see and touch. A model starts from random numbers and learns from a huge pile of text. Once trained, though, the model is very quick at something a child finds hard.
Many companies build models, and the numbers for each model change every few months. To keep things simple, this essay follows one model: Llama 3.1, which Meta released in 2024.3 From here on it is “our model.” The other big models are trained in broadly similar ways.
The essay follows both learners through four stages, side by side.
Two learners, four stages
1 · Before birth
A baby arrives with a brain built for learning. Our model starts out as random numbers.
Born with a brain that evolution spent billions of years shaping. Within months of birth, a baby already expects a solid object to stay solid.
Starts as billions of random numbers. Its first lesson, pre-training, has to build everything from scratch.
Babies have a head start. Young babies already expect certain things about objects, places, numbers and people. A baby looks longer, as if surprised, for example, when one solid object seems to pass through another.10
Our model gets no such gift. Before training, its weights are random. In pre-training, the model reads an enormous amount of text and guesses each next word. After every guess the weights shift a little, so the next guess comes out better. Everything the model learns ends up stored in those numbers.
Evolution passes its gift on in DNA. One copy is about 3 billion letters long. Our model’s weights take about a thousand times as much space to store.3,5 DNA is far too small to hold a copy of everything a child will know. Something in how her brain grows seems to make her a fast learner.
DNA is small next to our model
I think there’s something going on where pre-training is not like the process of humans learning, but it’s somewhere between the process of humans learning and the process of human evolution. We get many of our priors from evolution. Our brain isn’t just a blank slate.
Dario Amodei, head of Anthropic, interview, 13 February 2026.11
That’s why I call pre-training this crappy evolution. It’s the practically possible version with our technology and what we have available to us to get to a starting point where we can do things like reinforcement learning and so on.
Andrej Karpathy, AI researcher and a founding member of OpenAI, podcast interview, 17 October 2025.12
Ilya Sutskever doubts that evolution explains the whole gap. Evolution gave humans a lot for vision, hearing and movement, he says, “But in language and math and coding, probably not.” Children still learn these from far fewer examples than a model needs.13
Somehow a human being, after even 15 years with a tiny fraction of the pre-training data, they know much less. But whatever they do know, they know much more deeply somehow. Already at that age, you would not make mistakes that our AIs make.
Ilya Sutskever, co-founder and former chief scientist of OpenAI, interview, 25 November 2025.13
So whatThe child starts with a brain built for learning. Our model has to build its own way of learning out of data, and that takes a lot of it.
2 · Growing up
A child hears millions of words. Our model reads trillions.
Hears about 45 million words by age ten, and sees, touches and tries things all day long.
Reads about 11.7 trillion words, about 4,000 lifetimes of reading. Then it practises with rewards.
Side by side, the two piles of words are very different in size. A child’s words fit in a corner of one person’s lifetime of reading, and that lifetime fits in a corner of our model’s training text.2,3,4
A child hears millions of words, and our model reads trillions
Words are a small part of what a child takes in. Her eyes send a steady stream of data to her brain from the day she is born. By Yann LeCun’s way of counting, a four-year-old has seen about 30 times as much data as our model’s whole training text. A stricter count still gives about four times as much.3,16,17 Counted this way, the picture flips. Our model’s whole training text becomes the small square in the corner.
Our model’s whole training text is a corner of what a child sees
A child’s data also comes in a useful order. She chooses what to look at, picks things up and tries again when something surprises her, so each example teaches her more. A handful of pineapples is enough for her to know the next one.18,19,20 Today’s big models learn from images, sound and video as well as text.21 Our model still gets no say in what it reads next.
A brain and a model are built the opposite way round. A brain has about 100 trillion connections, roughly 250 times as many as our model has weights, and a lifetime of a few billion seconds to fill those connections.3,22
Our brains are very different. We only live for about two billion seconds. We don’t have trillions of experiences, just a few billion.
Geoffrey Hinton, winner of the 2024 Nobel Prize in Physics for work on neural networks, interview, 30 October 2025.23
After pre-training, our model gets a second stage of schooling, called post-training. It practises answering questions, and good answers are rewarded. Then its builders fix the weights and release it.3
So whatOur model makes up for a weak way of learning with a huge amount of reading. A child learns more from each example, and she gets richer examples.
3 · In a conversation
Here the model pulls ahead.
Holds about four things in mind at once. Needs days to read a long book, and keeps the gist.
Holds about a whole novel in its working memory, and the newest chatbots hold about eight. Uses a new example straight away.
How much can a model keep in view at once? Our model holds close to 100,000 words, about one long novel. The newest chatbots hold about 750,000 words, about eight novels.3,7,8
A user can paste the first four Harry Potter books, close to half a million words, into one of the newest chatbots. A person reading eight hours a day would need about four days to get through them.4 The chatbot takes them all in at once. A minute or two later it can answer a question about any page, or write a new scene in the same style.
Four days of reading, taken in at once
The same trick teaches a chatbot new skills. Given a team’s guide to writing reports, plus two good reports, a model can draft a third in the same style. Its weights stay exactly as they were. The new skill sits in the context. Researchers call this in-context learning.
The lesson lasts as long as it stays in the context.
If the guide drops out of view, because the chat grew too long or a new chat began, the model no longer has it. Tomorrow it will know the guide only if someone pastes it in again.
The weights stay locked, and the lesson lives in the context
People work the other way round. We humans hold about four chunks in mind at once, such as a word or a familiar phrase.6 Within a minute of hearing a sentence, most people have lost its exact words and kept its meaning.25 What people do keep can last for years.
Working memory, person and machine
The most striking test so far used a real language. Kalamang is spoken by fewer than 200 people in Indonesian Papua, and almost none of it is online. In 2024 Google gave one of its models a 573-page grammar of Kalamang, a word list and some example sentences, all in a single prompt. It translated English into Kalamang almost as well as a researcher who had studied the same book for weeks. It did worse translating the other way.21,27 Most of the help came from the book’s example sentences.28
How can a model learn without changing its weights? Pre-training reads so much text that the model ends up good at spotting patterns in whatever text it is shown. The slow learning of pre-training builds a fast learner.24
A slow loop builds a fast one
But I do think that anything that’s in the weights, it’s a hazy recollection of what you read a year ago. Anything that you give it as a context at test time is directly in the working memory.
Andrej Karpathy, podcast interview, 17 October 2025.12
So whatInside one conversation, the model is the quicker learner by far. The catch comes when the conversation ends.
4 · The rest of life
What a child learns at school on Monday is still with her on Friday. Our model’s weights stay as they were.
Keeps learning for life. Sleep helps turn the day into lasting memory.
Its weights stay fixed after release. Saved notes help, and a new version arrives months later.
People keep learning all their lives. A new employee picks up the job week by week and builds on what she learned the week before. The brain does this with two memory systems. One stores a new experience quickly, after a single exposure. The other learns slowly. During sleep the fast one replays the day to the slow one, which takes the lessons in a little at a time and keeps its older knowledge.9,30
Two memory systems in the brain, and a gap in the machine
Networks have no general way yet to copy a lesson from the context into the weights. When a network is trained on new material, the new learning tends to wipe out older skills. Researchers call this catastrophic forgetting. A network trained on thousands of tasks in a row slowly loses much of its ability to learn, until it does no better than a far simpler network.32,33 That is one reason companies leave the weights alone after release. As of October 2026, none of the big AI companies had announced a general model that updates its own weights from its conversations.
The chatbot’s software can still help. When a user tells a chatbot “keep it short, please,” the software may save that as a note. Next time it pastes the note into the context, and the model reads it there.34,35 Memory features, summaries of long chats and searches of saved files all work this way. They put text back in view, and the weights stay as they were.
What “keeping notes” means
The weights change only when a company trains a new version, months later. Some companies let users choose whether their chats may help train it.36
All learning is continual. It’s not a special phase. We always act and we learn. And that’s just the normal way of thinking. I’m not weird. The field is weird. They feel they need to call it continual learning. It’s just learning.
Richard Sutton, who shared the 2024 Turing Award for work on learning by trial and reward, Training Data podcast, 18 August 2026.37,38
So whatA model that cannot learn after release has to learn almost everything before it. That is a big part of why it needs so much data.
What’s missing
Researchers point to four abilities that today’s models lack.
A model would need to keep learning after release, and to learn from the physical world. It would also need to choose its own experience, as a child does, and to reason about problems unlike anything in its training. Each card below lists researchers at universities and AI companies who work on one of these four abilities, with their findings or arguments.
Four things still missing
Today’s models stop changing their weights once training ends.
Richard Sutton and his team trained networks on 2,000 tasks in a row. On an early task the networks scored 89 percent. By the 2,000th task they scored 77 percent, about as well as a far simpler network. The authors call this losing the “ability to learn on new examples.”33
Raia Hadsell and colleagues found a partial cure for forgetting in 2017. Their method “remembers old tasks by selectively slowing down learning on the weights important for those tasks.”32
In 2017 Chelsea Finn and colleagues trained a model on many small tasks so that it can pick up a new one from a few examples. In their words, the method “trains the model to be easy to fine-tune.”39
Demis Hassabis wants a learning method that “actually changes the model over time.” In January 2026 he said, “that technique has not been cracked yet.”40
“We cannot download the motor control signals of the robots from the internet,” Jim Fan said in 2024.41
Yann LeCun says language models “lack a model of the world.” “This is why we don’t have a domestic robot that is as agile as a house cat, or a truly autonomous car.”42
Fei-Fei Li calls language models “wordsmiths in the dark; eloquent but inexperienced, knowledgeable but ungrounded.”43
Sergey Levine borrows Plato’s cave: “The cave is the Internet, and the light shines from human intelligence, casting shadows of real-world interactions on the cave wall for the LLM to observe.”44
Rodney Brooks points out that “human dexterity relies on a rich sense of touch,” and videos of hands carry none of it. “Collecting just visual data is not collecting the right data.”45
David Silver runs the company Ineffable Intelligence. It is “creating a superlearner that discovers all knowledge from its own experience.”46
Young children pick much of their own experience. A model learns from whatever data it is given.
Alison Gopnik says children “are particularly adept at exploration.” She sees language models as “cultural technologies, like writing, pictures and print.”19
Linda Smith studies what babies see. “The data relevant to any one thing or event is sparse,” she says, and babies cope by steering their own input.18
Emmanuel Dupoux, Yann LeCun and Jitendra Malik titled their 2026 paper “Why AI systems don’t learn and what to do about it.” Their design switches between “learning from observation” and “learning from active behavior,” as animals do.47
Jürgen Schmidhuber has built curious machines since 1990. Since 1991 his machines have earned a reward when their picture of the world improves, so random noise is “no fun at all.”48
Pierre-Yves Oudeyer gave a robot a similar reward in 2007. The robot picked tasks that were neither too easy nor too hard, and moved on once it had mastered them.49
In 2025 OpenAI’s o3 beat people’s accuracy on text puzzles built on abstract rules. When Melanie Mitchell’s group checked its rules, about 29 percent fit the examples for the wrong reasons. For people the figure was 2.7 percent.50
Ilya Sutskever said in 2025: “these models somehow just generalize dramatically worse than people. It’s super obvious.”13
Melanie Mitchell calls this “jagged intelligence.” “In general, today’s AI systems perform extremely well until, often unexpectedly, they don’t.”51
Subbarao Kambhampati sees language models as “giant non-veridical memories,” meaning memories that can be wrong. Their answers “still need to be checked by external verifiers.”52
In 2020 Yoshua Bengio and Anirudh Goyal saw “a large gap” between machines and people when a problem looks unlike the training data.53
François Chollet warns that “unlimited priors or unlimited training data allow experimenters to ‘buy’ arbitrary levels of skills.”54
The answer
Each learner is quick at a different time.
The holy grail
A model could keep learning after release, from every conversation, the way a child keeps learning from every day. Researchers call this continual learning. A model like that would no longer have to learn almost everything up front, so it might need much less data. When will it arrive? The people building these models disagree.
You want to do it more than just having your data in the context window. You want to have something a bit deeper than that, which is, as you say, actually changes the model over time. That’s what ideally you would have. And that technique has not been cracked yet.
Demis Hassabis, head of Google DeepMind, January 2026.40
There’s a good chance that in the next year or two, we also solve that.
Dario Amodei, head of Anthropic, February 2026.11
They don’t have continual learning. You can’t just tell them something and they’ll remember it. They’re cognitively lacking and it’s just not working. It will take about a decade to work through all of those issues.
Andrej Karpathy, AI researcher, October 2025.12
Back at the breakfast table, the two-year-old learns from every conversation and keeps what she learns. A chatbot that did the same would learn from each talk with us humans and keep the lesson for the next day. If Amodei is right, that chatbot arrives around the toddler’s third birthday. If Karpathy is right, it arrives around her eleventh.