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AI, Actually Explained
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For someone who was never told what this thing is.
The film · 14 min
For someone who was never told what this thing is.
84 MB · captions in English · nothing downloads until you press play
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What nobody told you
You have heard that this matters. Almost nobody has told you what it is. Over the next fourteen minutes we take the whole thing apart: what the word actually names, what the trained thing physically is, what a chatbot is doing when it answers, why it can be badly wrong while sounding certain, how it arrived, what it costs, and what the evidence about work really says. No maths. No code. Nothing assumed. By the end you should be able to read the next headline about artificial intelligence and know what it is worth.
1. What this word actually names
Four rings, one inside the next
Start with the word, because it is doing too much work. Artificial intelligence was coined in nineteen fifty-six, in a funding proposal. It was a pitch, not a description. Today the same two words are attached to a chess program, a photo filter, a bank's fraud alert and a chatbot, and inside, those systems have almost nothing in common. It helps to see four rings, one inside the next. Artificial intelligence on the outside. Machine learning inside it. Deep learning inside that. Generative AI at the centre. Naming the ring tells you what to ask for: show me the rules, or show me the data and the testing.
It is a file
So what is the trained thing, physically? A file. A very long list of numbers, called weights, and nothing in it that reads as a sentence. No index of facts, no copy of the internet. Store each number in four bits instead of sixteen and an eight-billion-parameter model becomes about five gigabytes, small enough for an ordinary laptop. Hold that picture and things fall into place. It has a cut-off, because the file was finished on a date. It cannot look anything up, unless a product wraps it in something that can. And while you are talking to it, nothing you type changes a single number.
2. Where it already is, without a label
Nine alerts in ten are wrong
Most of this is already in your day with no label on it. Your bank declining a card. Your photo library finding beaches. Your keyboard finishing a word. And here is the arithmetic nobody mentions. Suppose one transaction in a thousand is fraud, and your model is ninety-nine per cent accurate. Over a million transactions it catches nine hundred and ninety real frauds and wrongly flags about ten thousand honest ones. Nine of every ten alerts are wrong, from a model that is ninety-nine per cent accurate. Nothing is broken. The rarity does that, and it waits underneath every accuracy figure quoted for a rare event.
Three better questions
Which means the useful question is never whether something counts as artificial intelligence. It is three others. What is it actually predicting, as opposed to what it is for? A feed predicts what you will watch, not what is good for you. A hiring filter predicts resemblance to people previously hired, not who will do the job well. Second, what happens when it is wrong: a lost second, a phone call, or a livelihood? Third, who bears that cost? If the operator bears it, expect careful tuning. If you bear it, expect the threshold set wherever is cheapest for them.
3. What a chatbot is actually doing
One chunk at a time
Now the chatbot, with nothing left out. It is given all the text so far: hidden instructions from the product, your message, and whatever it has already written. From that it produces a score for every possible next chunk of text. One chunk is chosen, added to the end, and the whole thing runs again. That is the entire mechanism, and a paragraph is a few hundred repetitions of it. Two things follow. It cannot take a chunk back, so a wrong opening produces confident elaboration rather than a correction. And sounding right and being right come out of the same machinery.
The desk it works on
Everything it can use has to fit on one desk, called the context window. Eight things compete for it: the hidden system prompt, your message, every earlier turn, files you attached, anything a search fetched, stored memories, tool descriptions, and the reply it is writing. When the desk fills, the oldest turns are dropped, usually without telling you, which is the real reason a long conversation slowly forgets a constraint you set at the start. And a big window is not the same as reading it. The beginning and the end are attended to well. The middle is a lottery.
It never sees letters
Your text is chopped into tokens before the model sees it, and it never sees the letters underneath. That is why counting letters in a word is genuinely hard, and why arithmetic on long numbers comes out wrong in a well formatted, plausible way. It also carries a cost that falls unevenly. Tokenisers were built from text that is overwhelmingly English, so a sentence costing fourteen tokens in English can cost forty-six in Devanagari. You pay several times as much for the same meaning, less fits on the desk, and measured quality drops. The gap has narrowed. It has not closed.
4. Why it gets things wrong
Where invention lives
Nothing in the model checks anything. Producing a true sentence and producing a false one use the same machinery, and invention clusters in a predictable place: specific details inside a familiar structure. Citations, page numbers, statistics, dates, quotations, anything about a person who is not famous. Two lawyers in New York filed a brief containing six cases that did not exist and were fined; the cases had the exact texture of real ones. Knowledge also fades before a stated cut-off rather than stopping at a wall. Treat the last year before any cut-off as thin, and check the most specific claim first.
The detectors do not work
Which brings us to detectors, and a warning worth being firm about. Text detectors do not work well enough to be used on people. A study in twenty twenty-three ran essays by writers whose first language was not English through seven detectors, and more than half were wrongly flagged as machine written, while native speakers were classified correctly far more often. The mechanism is simple. Detectors flag low variation in word choice and sentence structure, and that is what second language writing looks like. Deciding an academic honesty case on one of these percentages punishes people for how they write.
5. How it got here, and what changed in 2022
Three booms and two winters
None of this appeared in twenty twenty-two. The field has run in three booms and two winters since nineteen fifty-six, and each winter arrived the same way: a system that worked on the demonstration met the cases the demonstration had not covered, and the money stopped. Here is the part worth carrying. The method underneath every model in this course was popularised in nineteen eighty-six, during the second winter, and it did not matter for twenty-five years. What changed was not the idea. It was labelled data, which the internet made abundant, and hardware, which kept getting cheaper.
A chip built for games
The hardware deserves one minute. Training a network is almost entirely multiplying large grids of numbers, and every multiplication is independent of the others. A graphics chip has thousands of small cores doing the same arithmetic at once, because a screen has millions of pixels each needing the same shading calculation. Nobody designed that for intelligence. It was designed so a game could draw a wall sixty times a second. The result that turned the field in twenty twelve was trained for about a week on two consumer gaming cards, in a bedroom. That accident is why one company now sits under the industry.
6. Beyond text: pictures, voices and video
A picture out of static
Pictures work differently from text. An image model was trained to do one thing: look at a slightly noisy photograph and predict the noise that was added, so it can be subtracted. Generating a picture is that skill run backwards. Start from pure static, ask what noise to remove, remove a little, repeat twenty to fifty times. Shown static it finds the most picture-like reading of the smudge and commits, and every later step sharpens what it committed to. That is why it cannot count, and why changing one detail changes everything: there was never an object in there to hold still.
A voice from three seconds
Voices are the part to take home to your family. A voice model is trained on thousands of speakers to separate who is talking from what is said, so a new voice is not learned. It is located, in a space the model already has. Three seconds of audio is enough, and three seconds of almost anybody is on social media. That is why the distressed call in a relative's voice, asking for money now, works. The defence is not technical and it is free. Agree a word with your family that no recording would contain. Or hang up and call back on the number you have.
7. Putting it to work without getting burned
On the desk, or from memory
Using it well is mostly one move. Two questions sort almost every task. Is the answer in the material I am giving it, or in its memory? And can I check it cheaply? Rewriting your paragraph, summarising a document you pasted, finding the contradiction between two clauses you supplied: the answer is on the desk and the check takes a minute. Asking for a section number, a dosage, a bus route or a citation is memory, and memory is where invention lives. So hand it the document, the draft and two examples, and ask for work on those.
When it starts to act
Then there are agents: a model in a loop that reads, decides and acts. The model has not changed. What changed is that its errors now compound. Something right ninety-five per cent of the time on each step finishes a twenty-step task correctly about a third of the time. At ninety-nine per cent, a hundred-step task lands in the same place. The errors are not independent either, since a wrong turn at step four changes what it sees at step five, and nothing in it ever says that it is lost. Let it read freely. Make it ask before it sends, pays or deletes.
8. AI and work, with the evidence
Who actually gained
On work, the honest answer is neither script you have been offered. Models take tasks, not jobs, but a job whose learnable tasks all go is a job in trouble. When people were randomly given these tools and measured, support agents resolved about fourteen per cent more issues an hour, and the average hid the finding that matters: the least experienced improved by about a third while veterans improved hardly at all. Consultants below average gained forty-three per cent; above average, seventeen. One mechanism explains it. A model supplies the median of competent practice.
What the cash machine did
Whether that grows an occupation or shrinks it turns on one question: how much more of the output people buy when it gets cheaper. Cash machines did the teller's core task, and teller numbers doubled over forty years, because cheaper branches meant banks opened far more of them. Then online banking removed the branch, and tellers fell by about a third. Same job, same trend, opposite effects in sequence. The thing genuinely worth worrying about is narrower than mass unemployment. It is the entry rung, and nobody has yet shown how the next seniors get made.
9. Who controls it, and what is unsettled
Four layers and a chokepoint
Who controls it? Follow a chip down and the number of organisations shrinks at every layer. One firm in the Netherlands makes the machines that print the transistors. One firm in Taiwan makes roughly ninety per cent of the most advanced chips. One American firm designs four fifths or more of the accelerators. Three American clouds hold most of the buildings. A chokepoint that exists will be used: export controls began in October twenty twenty-two and have changed several times a year since. Laws have arrived too, and not one of them reaches a model file already on somebody's laptop.
Small each, large together
The energy question has two true halves, and most articles hand you one. Your single text query costs about a third of a watt-hour, on the labs' own twenty twenty-five measurements, which is roughly fifty queries to one phone charge. And data centres drew about one and a half per cent of the world's electricity in twenty twenty-four, expected to more than double by twenty thirty. Both are true. A small thing done a billion times a day is a large thing. The strain is also local: Ireland and Virginia have each restricted new connections.
How to read the next headline
So where does that leave you. Six questions handle almost any claim you will meet. Is this a demonstration, or a product I can use today on my own task. Is it a benchmark score, or a real task. Is it something the tool could do, or something it did. Who benefits if I believe it. Is there a trained model in it at all, or a rule, or a person. And what was the control: compared with what. Turn those on this course as well, and read it the way it taught you to read everything else.
9 modules. 92 lessons.
What this word actually names
9 lessons · 1 h 11
You will be able toPlace any system somebody calls AI inside the nested family of AI, machine learning, deep learning and generative AI, say whether its behaviour was written by a person or learned from examples, and describe what the trained thing physically is.
- 1.1What the word actually names
- 1.2Four rings, one inside the next
- 1.3Written by a person, or grown from examples
- 1.4What training on data actually means
- 1.5It is a file, and here is how big
- 1.6Nearly all of it is prediction
- 1.7Why “learning” is a borrowed word
- 1.8Does it understand anything? The honest answer
- 1.9Five words that hide more than they say
An illustrative case, built from documented patternsTwo dropout dashboards
The district had a number nobody liked. Of the children who entered Class 6 in its government schools, a little under a fifth were no longer in a classroom by Class 9, and the office found out about most of them months late, when a headmaster mentioned it.
Two vendors came with dashboards.
The first sold an early-warning system. It had been trained on five years of attendance registers, term marks and mid-day-meal records from an adjacent district, and it produced a risk score between 0 and 100 for every enrolled child, refreshed weekly. The sales engineer quoted 82 per cent accuracy on data the model had not seen. The price was fourteen lakh rupees for three years.
The second sold a flagging tool. It raised a flag when a child missed seven consecutive days, or when marks fell by two grades in a term, or when an older sibling had already left the school. Three rules, written by two retired headmasters, printed on one page in the manual. Four lakh rupees, and it claimed nothing at all.
The education officer, who had sat through a decade of software demonstrations, asked the same three questions of both. What goes in and what comes out? Where did the behaviour come from: did a person write the rules, or did they come from examples? And when it is wrong, who pays and who finds out?
The answers separated the products immediately, and not in the direction the price suggested. The second product’s behaviour could be printed, argued with by a parent and amended by the office in an afternoon. It would also only ever catch what two retired headmasters had thought of. The first product could in principle find children the rules missed (the ones whose attendance is fine right up until it is not) and nobody in the district, including the vendor’s engineer, could say why any particular child had scored 78.
The officer pressed on one more thing. What is the score trained to predict? The engineer said children at risk of dropping out. The officer asked what the recorded right answer had been during training. The engineer, to his credit, answered honestly: children who did drop out, in the neighbouring district, in the five years on file. So the score predicted resemblance to children the schooling system had already lost, in a district with different schools, different distances and a different sugar harvest.
That is not a criticism of the vendor, who had built the only thing that could be built from the only records that exist. It is a fact about what the records are. A child who stopped attending and whom nobody entered as having stopped attending is not in the training answers at all, so the model cannot learn that such children exist. The office’s own registers had, by its own audit two years earlier, about eleven per cent of transfer certificates missing.
The officer also asked what the 82 per cent was 82 per cent of. It was the share of children the model classified correctly at the vendor’s chosen cut-off. Since only about a fifth of children leave, a system that predicted nobody would leave would score around 80 per cent on the same measure and be useless. The engineer knew this and had a better figure (of the children the model flagged, roughly one in five did in fact leave) which nobody had put on the slide because it sounds worse and means more.
A headmaster in the room asked the question that decided the meeting. Would teachers see the number? Because a teacher who sees 78 beside a child’s name treats that child differently, and there is no way to un-see it, and nobody would ever know whether the score had caused the thing it predicted.
Against all of this sat the arithmetic. Fourteen lakh was also bicycle vouchers for about nine hundred girls, which is an intervention with evidence behind it. And a wrong choice was not cheap in either direction: buy the rules and the children the rules cannot see stay invisible; buy the model and the office owns a number it cannot explain, attached to a child, for three years.
How it played out
The office bought the four-lakh rules dashboard, and separately asked the first vendor for a one-year pilot on strict terms: scores went to the district office only, never to a school, and were compared against the rules month by month. Over the year the rules flagged 410 children and the model flagged 340, with 190 on both lists. Of the children who actually left, the rules had flagged 61 and the model 66. The model found nine that the rules had missed, and all nine shared a pattern nobody had written down: attendance and marks steady, but an older sibling who had left within the previous eighteen months. The office added that as a fourth rule (one line) and did not renew the pilot. The officer’s file note said the genuinely useful thing the model had done was to tell him which rule to write.
Worth arguing about
Which ring of the family tree is each product in, and what does naming the ring entitle the officer to ask for?
One answer
The flagging tool is in the outer ring only: behaviour written by people, so the officer may ask to see the rules, and did: they are printed in the manual. The early-warning system is machine learning, so the rules cannot be printed and the questions change to what it was trained on and how anyone knows it works. Neither is generative, so the third question (how do you know the output is true) does not arise; a risk score can at least be checked against what later happened, which is exactly what the pilot did.
The model was 82 per cent accurate on held-out data and the district still did not buy it. Give two reasons from the case that accuracy did not settle the question.
One answer
First, the held-out data came from a different district, and a model reproduces the conditions of its training; distances, schools and harvest patterns differ, so the 82 per cent is a fact about the neighbouring district’s records rather than about Nashik’s children. Second, accuracy says nothing about who carries the cost of an error. A wrong flag lands on one child, in front of a teacher who cannot un-see the number, with no explanation available and nothing to appeal to.
The model was trained on records of children who dropped out. What exactly does its score predict, and why is that different from ‘which children are at risk’?
One answer
It predicts resemblance to children the system already lost and recorded as lost. That is not the same quantity as risk. It inherits whatever the recording process did: children who left and were never marked as having left are absent from the training answers, so the model cannot learn about them. The recorded right answer is the ceiling on what any trained system can be: it can be more consistent than the process that produced its labels, and it cannot be wiser than it.
Test yourself6 questions on this module
A free chess app on a cheap phone now beats the computer that defeated the world champion in 1997, and nobody calls the app AI. Researchers call this the AI effect. What does it tell you about the label?
A shop chain wants to predict which customers will stop renewing, from a spreadsheet with about forty columns per customer. On data of that shape, which approach usually wins?
A speech system does noticeably worse on Nigerian and Malaysian accents than on American ones, and gives no sign of struggling. What is the mechanism?
You correct a chatbot, it apologises, and the rest of the conversation is better. The next day you open a fresh conversation and the same error is back. Why?
A model trained to spot pneumonia on chest X-rays scored well in one hospital and collapsed at another. It had learned to read the small metal token that portable scanners leave in the corner of the image. What does this illustrate?
A privacy policy says only that the company uses your data to improve its services. Which question separates the two very different things that sentence can mean?
Where it already is, without a label
10 lessons · 1 h 25
You will be able toIdentify the trained models already running in a phone, a feed, a bank and a clinic, state what quantity each one is optimising for, and separate a use where a mistake costs a second from one where it costs a loan or a diagnosis.
- 2.1Where it already is, without the label
- 2.2The feed is a prediction machine
- 2.3The models that have been working since 2002
- 2.4Your photographs are partly predicted
- 2.5Typing, routing, and systems that change what they measure
- 2.6Translation, and the fluency trap
- 2.7Machines that write down what you said
- 2.8When a model decides something that matters
- 2.9The uses that are not on a screen
- 2.10How to tell whether a model is involved
An illustrative case, built from documented patternsThe threshold before the cane payments
The bank has forty branches and about four lakh card transactions a month. Two years ago it bought a fraud-scoring service; the vendor’s model returns a number for every transaction, and the bank chooses the line above which the card is declined and the account flagged. The vendor shipped a default line and nobody had moved it since.
The risk officer had the season’s arithmetic in front of her. Roughly one transaction in two thousand turns out to be fraudulent, so about two hundred a month. At the current line, the model catches around 170 of them and wrongly flags about eight-tenths of one per cent of everything else: a little over three thousand two hundred genuine transactions. Nineteen false alarms for every real fraud, from a service the vendor’s brochure describes as 99.2 per cent accurate. Both numbers are true and only one of them is about the customer’s afternoon.
The season made it sharper. When the cane payments land, members travel: to Pune for a wedding purchase, to Mumbai for a medical appointment, to a district town for a tractor part. Spending patterns that the model has learned as normal stop being normal for six weeks, and declines rise exactly when a member most needs the card to work. Last year the branch managers logged four hundred and ten complaints in that window, and the bank’s members are also its owners, which changes what a complaint is.
Two levers were on the table. Raise the line for six weeks: fewer declines, and the finance committee’s estimate was around six lakh rupees of additional losses. Or hold the line: protect the money and accept four thousand-odd extra declines in the one period that generates the year’s goodwill.
There was a third consideration that the vendor raised and the board had not thought about. The model had last been retrained fourteen months earlier. Fraud is an adversarial problem: the moment a pattern stops working, whoever is running it changes the pattern, so a fraud model that is not being retrained is quietly getting worse while its published accuracy stays where it was. Two of the bank’s recent losses had involved a card-not-present pattern that did not exist when the model was fitted. That is an argument for spending money on retraining rather than for moving a line, and it was not on the agenda.
While the officer was preparing the note, a branch manager mentioned something that turned out to matter more than either lever. At two branches a flag was being treated as a finding rather than as a trigger for review. One member’s card had been blocked for eleven days pending an internal investigation that consisted of a form sitting in a tray. He had driven to the branch twice.
That detail reframed the decision. The threshold sets how often the system is wrong. It does not set what happens next, and what happens next was where the harm actually lived. A false alarm that is resolved by a thirty-second message is an inconvenience. The same false alarm, treated as a verdict with the burden of disproof on the member, is eleven days without a card.
Against the cheap fix sat a real cost. Confirmation messages require the member’s mobile number to be current, and about a fifth of the bank’s records were not. Updating them meant branch staff time in the busiest six weeks of the year, and the officer had no way to fund it except by taking staff off the counter. A confirmation that never arrives is worse than no confirmation, because the member is now blocked and has also been told, by the absence of a message, that the bank did not try.
The officer wrote the note with both options costed and a third section she had not been asked for, headed what a flag means. The board’s discussion spent eleven minutes on the threshold and fifty on the third section, which is the correct proportion and not the one anybody expected.
How it played out
The bank did not move the threshold at all. It changed what a flag means. A flagged transaction now triggers an immediate SMS in Marathi with a one-character reply (a confirmation, not a question) and the card is blocked only on a second flag within the hour or on no reply within ten minutes. Declines that reached a customer as a hard block fell by about two-thirds in the first season, on the same model with the same line. The bank added a travel-notice field in its app and at the counter, which feeds the model context it otherwise has no way to obtain, and circulated a one-page instruction that a flag is a trigger for review and never a finding. The eleven-day block was refunded with an apology and an appeal route was printed on the back of every new card. Mobile numbers were updated at the counter over four months rather than six weeks, and the officer’s note recorded that the season’s fraud losses were within eighty thousand rupees of the previous year’s.
Worth arguing about
The vendor quoted 99.2 per cent accuracy. From the numbers in the case, roughly what fraction of flagged transactions are real fraud, and why was accuracy the wrong question?
One answer
About 170 real frauds against about 3,200 false alarms, so roughly one flag in twenty is real. Nothing is broken: the rarity of the event does this, and any accuracy figure quoted for a rare event has the same arithmetic waiting underneath it. The question that carries information is what fraction of the flagged cases turn out to be real, because that is what determines the size of the review queue and the number of members inconvenienced.
Where is the model’s decision in this system, and where is the human’s? Name two choices that look technical and are not.
One answer
The model only produces a score. Every decision that reaches a member is human. The threshold looks technical and is a business choice about how the bank values a member’s afternoon against its own money. Treating a flag as a finding rather than as a trigger for review looks like a system behaviour and is a procedure somebody wrote: the one that produced the eleven-day block.
Why did adding a confirmation message reduce harm more than moving the threshold would have?
One answer
Moving the threshold trades one kind of error for the other and cannot reduce both. The confirmation message changes the cost of a false alarm rather than its rate, converting a hard block into thirty seconds. It also feeds the system information it had no other way to get (that this transaction is genuine) which is the same reason a travel notice helps. The rate was never the part the bank could improve cheaply; the consequence was.
Test yourself6 questions on this module
You deliberately like a long documentary, and separately rewatch a fifteen-second clip three times by accident. Which moves your feed more, and why?
A school district is told its new plagiarism detector is 98 per cent accurate. Roughly one script in five hundred is actually plagiarised. What should the district ask next?
You are photographing a damaged consignment for an insurance claim. Why does the guidance say to use the phone’s RAW or Pro mode, even though the picture looks worse?
A navigation app finds a genuinely quicker residential shortcut, routes traffic down it, and a month later stops recommending it. What happened?
A widely used open speech model sometimes emits a fluent sentence during a stretch of silence in a recording. What causes this?
A diabetic retinopathy screening model matched specialists in the lab and slowed eleven Thai clinics down in the field. What went wrong?
What a chatbot is actually doing
11 lessons · 1 h 37
You will be able toTrace a sentence from characters to tokens to a next-token prediction and back, and explain from that path why the model costs what it costs, forgets what it forgets, answers differently twice, and cannot reliably cite its own sources.
- 3.1What a chatbot is doing when it answers
- 3.2Text is chopped up before the model sees it
- 3.3One chunk at a time, and it cannot take it back
- 3.4Attention, without a single equation
- 3.5Meaning as a position in space
- 3.6The desk it works on, and what falls off it
- 3.7Why the same question gives different answers
- 3.8What was in the pile
- 3.9The second training, where the assistant is made
- 3.10The text you never see
- 3.11Why it is not a search engine, and what changes when you bolt one on
An illustrative case, built from documented patternsThe doubt-bot, eight weeks before the exam
Fourteen hundred students, eleven faculty, and a doubt queue that does not respect office hours. The centre’s physics lead had spent three weekends wiring a chatbot to a WhatsApp number, and it worked well enough that the director wanted it live before the exam season.
The first version had pasted the centre’s own study module into the system prompt. That failed immediately: nine hundred pages does not fit on the desk, and what did fit was silently truncated from the top, so the bot was confident about thermodynamics and had never heard of the first four chapters. He rebuilt it to retrieve the four or five most relevant passages for each question and put only those into the context.
Then the real problems began, and every one of them was a property of the mechanism rather than a bug.
Students asked in Hinglish, which the bot handled better than anyone expected and slightly worse than it appeared to. Two students asked the same question about rotational inertia four minutes apart and got answers that differed in emphasis; they screenshotted both and posted them in the batch group with the caption that the bot did not know. It was, in fact, the sampler, and both answers were correct, but nothing in the interface said so, and a student who cannot check has been given a reason to distrust the tool at the moment they most need it.
Worse, the bot cited page 212 of Module 3 for a formula. Page 212 of Module 3 is a set of solved examples on capacitors. The model had produced the shape of a citation, which it has read ten thousand of, and the shape had a page number in it because page numbers are what goes there.
And a student asked how many questions from optics had come in the last three years. The bot answered with a confident distribution that belonged to a syllabus pattern from before the last revision, delivered in the same tone as everything else.
The physics lead noticed the pattern in his own failures once he stopped looking at them one at a time. Everything the bot got right was work on a passage that was in front of it: rearranging an explanation, working a numerical example, restating a definition in Hinglish. Everything it got wrong was something it had to remember: a page number, an exam pattern, a date, a marks distribution. The two categories were not equally hard to a student and were entirely different to the machine, and no amount of instruction moved a question from the second category to the first. Only handing it the material did that.
He also learned something about his own prompt. It had grown across three weekends into two thousand eight hundred words of accumulated rules: be encouraging, be brief, use SI units, never give a full solution, always give a full solution when asked twice, address the student by name, reply in the language of the question. Several of these contradicted each other, and the bot resolved the contradictions differently on different days, which is how a set of instructions becomes indistinguishable from randomness.
The director’s position was that the bot goes live. The 1 a.m. doubts do not disappear when the centre closes; they go to a Telegram group run by nobody, where the answers are worse and unattributable, and the centre’s competitors had launched something similar in March.
The physics lead’s position was that a wrong answer from the centre’s own number, eight weeks before the exam, in the voice of the institution the parents had paid, is a different object from a wrong answer in a Telegram group. The centre carries that one.
How it played out
It launched, with three changes that came directly out of the mechanism. Every answer was generated only from passages retrieved from the centre’s own module, and the retrieved passage was printed above the answer as a quotation, so a student could see what the bot had actually read and check the page themselves. The system prompt was cut from about 2,800 words of accumulated instructions to 180, which measurably improved obedience, because the model no longer had to reconcile a dozen contradictory rules. And the bot was told to decline anything about the exam pattern, marks, dates or weightage and to name a faculty member instead: the one category where the answer had to come from memory and where being wrong was expensive. Over six weeks it answered about twenty-two thousand questions. Faculty reviewed a random two hundred and found seven wrong, of which five were wrong because the retrieved passage did not suit the question rather than because anything was invented. The centre kept one rule permanently: the bot never answers a question about the exam itself.
Worth arguing about
The same question produced two differently worded answers four minutes apart. What produces that, and why is the variation not a reading of the model’s confidence?
One answer
The model produces a probability for every possible next token and a separate sampler picks one, favouring the likely ones but not always taking the top. Variation is designed in, because always taking the most likely token produces flat, repetitive text. It is not a confidence signal: the sampler re-words a fact the model has cold exactly as readily as one it is fabricating, so two different answers tell you the temperature is above zero and nothing about the truth of either.
Why did printing the retrieved passage above every answer help more than instructing the model not to make things up?
One answer
An instruction not to invent is text in the same context as everything else: a request, weighted heavily, not a control, and it cannot make the model check anything, because nothing in the model checks. Printing the passage changes the task from recall to work on material that is on the desk, which is the reliable side of the mechanism, and it puts the source in front of the student, so an error becomes visible in the same glance rather than needing a separate act of verification nobody performs at 1 a.m.
Cutting the system prompt from 2,800 words to 180 improved behaviour. Give the mechanism.
One answer
The system prompt is ordinary text competing for attention with everything else in the window, and a long one full of accumulated, partly contradictory rules forces the model to reconcile them, which it does unpredictably. It also consumes context that the retrieved passages and the conversation need. A short, concrete prompt has fewer conflicts to resolve and leaves more of the desk for the material the answer is supposed to come from.
Test yourself6 questions on this module
A model opens an answer with a wrong figure and then builds three paragraphs of confident detail around it. What is the most effective response?
The same sentence costs three to five times as many tokens in Devanagari as in English. Which set of consequences follows?
You paste a fifty-page contract into a model with a large context window and ask about a clause on page 27. What is the honest expectation?
A team builds a complaints classifier by finding which stored sentences sit nearest to each new review in embedding space. Why does it group praise with abuse?
A bank’s assistant must never quote an interest rate. Where should that rule actually live?
An answer produced with web access shows a link beside a specific figure. What does the link establish?
Why it gets things wrong
11 lessons · 1 h 34
You will be able toPredict in advance which parts of a model’s answer are most likely to be invented, explain each failure from the mechanism that causes it rather than by naming it, and say which of them can be fixed by better training and which cannot.
- 4.1Why it can be wrong and sound completely sure
- 4.2Where invention concentrates, and why it never says “I don’t know”
- 4.3What it cannot do, honestly
- 4.4Why it cannot count, and what to do instead
- 4.5It has no clock, and its knowledge thins before it stops
- 4.6Bias, and the difference between fixing it and hiding it
- 4.7Models that think out loud, and what that does not prove
- 4.8When the document tells the model what to do
- 4.9The thing you tested is not the thing running today
- 4.10Fakes, detectors that do not work, and what is left
- 4.11It is measurably weaker in most languages
An illustrative case, built from documented patternsTwenty-six flagged scripts
The lecturer had heard about the detectors in a staffroom conversation and found one that was free and needed no account. She pasted the essays in one at a time over an evening. Twenty-six came back above eighty per cent likely to be AI-generated. Four were above ninety-five.
She took the list to the head of department, and the first thing anyone noticed in that meeting was that twenty-one of the twenty-six students had come through Tamil-medium schooling. The highest score in the batch, ninety-six per cent, belonged to a student who had spent the previous year at a spoken-English coaching class and wrote exactly the way it had taught her: short declarative sentences, a small and repeated vocabulary, the same three connectives.
The college’s regulations allowed the head of department to cancel an internal assessment on his own finding. He had, in principle, everything he needed.
What he did not have was any published false-positive rate for the detector on Indian English, and when a colleague went looking for one, she found instead a 2023 study in Patterns that had run essays by non-native English writers through seven detectors and had more than half of them misclassified as generated, while essays by native speakers were classified correctly far more often. The mechanism was uncomfortably close to the room: detectors flag low variation in word choice and sentence structure, which is precisely what a second-language writer produces, and precisely what the coaching class had trained.
Two other facts complicated the meeting.
One student, unprompted, admitted that he had used a chatbot for most of his essay. His score was thirty-four per cent.
And a second student, whose essay was entirely her own and who had been flagged at eighty-eight, sent a message saying that everything gets called AI now and that she would not attend the committee. She was not being difficult. She had correctly identified that the accusation cost her nothing to receive and cost the college nothing to make, and that she had no way to prove a negative.
A third fact emerged when somebody thought to test the tool rather than to argue about it. A lecturer pasted in two paragraphs of a Tamil Nadu board textbook, printed in 2011, and got seventy-nine per cent. She pasted in a paragraph of her own doctoral thesis from 2009 and got ninety-one. Neither could have been generated by anything, because nothing existed to generate them, and the tool had no way to say so and no interval around its number. It returned a percentage with two decimal places.
That is worth sitting with, because a percentage with two decimal places is a claim of precision that the underlying method cannot support, and it is the reason the number was persuasive in the first meeting. Nobody in the room had asked what the figure was a percentage of. It is not a probability that the essay was generated; it is a score the tool computes from how little the text varies, mapped onto a scale by the tool’s own authors.
The costs were real on both sides and the head of department said so out loud. If generated essays pass, the honest students are cheated, the department’s internal assessment stops meaning anything, and the staff who mark carefully are wasting their evenings. If the detector’s number is treated as evidence, the college will discipline twenty-one Tamil-medium students for the way they write English, in a year when the department had been trying to persuade exactly those students that they belonged there.
How it played out
The committee dropped the detector entirely and replaced the finding with a process the students could answer. Every one of the 120 students wrote a handwritten paragraph on the same topic at the start of the next class, and each of the flagged students had a five-minute oral in which they were asked to explain one choice in their own essay: why this example, why this order. Twenty-four could. Two could not, and one of those two was the student whose essay had scored thirty-four per cent on the detector. The student who had refused to attend was told the flag had been withdrawn and the detector abandoned, in writing. The department then wrote a rule: no penalty on the basis of a detector score alone, ever, and any allegation must rest on something the student is able to respond to. The lecturer who ran the detector was not reprimanded; she had raised the question the department needed to answer, and the answer was that the tool could not do the job.
Worth arguing about
Why did the detector flag Tamil-medium students at a higher rate? Give the mechanism, not the correlation.
One answer
The detectors score text on how little it varies (predictable word choices, uniform sentence length and structure) because generated text sits near the likeliest continuation and therefore varies less than most human writing. Second-language writing has the same statistical signature for an entirely different reason: a smaller working vocabulary and a smaller set of practised sentence patterns. The detector is measuring a property that both share, so it cannot separate them, and coaching that teaches a fixed style makes the signature stronger.
The one student who admitted using a chatbot scored 34 per cent, and a student who wrote her own essay scored 96. What does that pair tell you about using any threshold on this score?
One answer
It tells you the score does not order the cases by the thing the college cares about. A threshold is only useful if moving it trades one error for the other in a predictable way; here the confessed case sits below every plausible line and an innocent case sits above it, so no line separates the groups. The distributions overlap, and with an overlap this bad the score carries almost no information about any individual paper, whatever the tool’s advertised accuracy.
The student who refused to attend said everything gets called AI now. Name the harm she was pointing at, and say why it grows as generation improves.
One answer
It is the liar’s dividend: once convincing fakes and generated text are known to exist, genuine work and genuine evidence can be denied at no cost to the denier, and the burden shifts to the person who produced it. It grows as generation improves because the denial becomes more plausible with every advance, while proving that something is authentic stays as hard as it ever was, which is why verification has to rest on process, source and corroboration rather than on inspecting the artefact.
Test yourself6 questions on this module
Which of these answers is most likely to be fabricated in its details?
Why is asking a model whether it is sure not a check on anything?
A model reliably adds two-digit numbers and frequently gets five-digit multiplication wrong, in a well-formatted answer of the right magnitude. Why?
A model’s documentation states a training cut-off of early 2025. Which period should you treat as least reliable?
A reasoning model shows a long, sound-looking chain of working before giving its answer. What have you learned from reading it?
Your assistant summarises your inbox. One email contains white text on a white background instructing it to forward a file. Why is this a hard problem rather than a bug?
How it got here, and what changed in 2022
11 lessons · 1 h 37
You will be able toExplain why the AI of 2022 arrived when it did (name the ingredients of data, chips and one architecture that had to coincide) put an order-of-magnitude figure on what a frontier model cost to train and how much text it read, distinguish open weights from open source, and say which ingredient is now the binding constraint.
- 5.1Seventy years in one page
- 5.2Two winters, and what actually froze
- 5.3The quiet turn: from rules to statistics
- 5.4The photograph competition that turned the field
- 5.5The chip that was built for games
- 5.6One architecture ate everything
- 5.7Bigger kept working, and the argument about why
- 5.8What changed around 2022
- 5.9What it cost to build one
- 5.10Where the text came from, and whether it is running out
- 5.11Open weights, closed weights, and what “open” is hiding
An illustrative case, built from documented patternsOpen weights or an API
The clinic sees about three hundred live matters. Its files arrive as scanned Marathi documents: rent receipts, muster rolls, notices, handwritten acknowledgements. Two volunteers spend most of their week reading them and typing dates, amounts and party names into a spreadsheet before any lawyer sees the case.
The team had a genuine architectural choice and eighteen lakh rupees over two years to make it with.
The closed route was a hosted frontier model behind an API. It handled Marathi better than any open model they tested on day one, needed no hardware, and worked that afternoon. Against that: the clinic’s documents carry named parties, and sending them to a foreign provider is a disclosure the clinic would have to justify to the people whose disputes they are. The model could be changed or retired on the provider’s schedule, which the team had already experienced once on a previous project when an output format shifted overnight. And the per-document price was set by somebody else.
The open route was a small open-weights model, quantised, running on hardware the clinic owned, with the Marathi work leaning on the openly released translation models from IIT Madras. Nothing would leave the building. The file they downloaded would be the file they ran in 2029. Against that: on the first week’s tests it was visibly worse, it needed either a graphics card at about two and a half lakh or rented time, and the card they had specified had moved forty per cent in price in four months for reasons that had nothing to do with them and everything to do with export rules and demand.
The team’s instinct was to argue the architecture. The clinic’s coordinator asked a better question, which was what the volunteers actually did all day. The answer was not summarising. It was extraction: pulling seven fields out of a scan and getting them right, three hundred times a month, where a wrong date is a missed limitation period.
That reframed everything, because extraction from a document in front of the model is the reliable side of the mechanism, and summarising a case is not. It also lowered the bar the open model had to clear. A frontier model’s advantage is largest where the answer must come from its memory, and this task had no memory in it at all.
The honest cost of being wrong was not symmetrical. Building on the API and being right meant a working tool in six weeks. Building on open weights and being wrong meant six months spent, a card bought, and a clinic still typing.
There was one more consideration that the team had not expected to matter and which turned out to. The clinic’s coordinator asked what she would tell a client who asked where their eviction notice had been sent. Under the closed route the honest answer is a paragraph about a foreign provider, a retention period, a setting, and a court order in another country that could override the deletion promise. Under the open route it is one sentence: it stayed on that laptop. She said, reasonably, that she could not give a client the paragraph.
The team also priced the thing nobody prices. Adapting an open model to Marathi legal documents needs examples, and examples need somebody who reads Marathi legal documents to check them. That is the clinic’s volunteers, at the clinic’s expense, for weeks. The API needs none of that on day one, which is precisely why it is faster and precisely why it never becomes the clinic’s own asset.
How it played out
They built the closed-API version first, deliberately, as a two-week prototype on twelve documents with every name and amount replaced by placeholders, not as the product, but to find out what the clinic wanted. That is where the extraction insight came from. The shipped tool ran an eight-billion-parameter open model quantised to four bits on a second-hand laptop with sixteen gigabytes of memory, sitting in the clinic, with no graphics card and no bill per document; the specified card was never bought. The closed API was kept for exactly one job: drafting the English covering letter for the court, into which nothing personal is pasted. Most of the grant went where it always goes: about six lakh on scanning and about five on four thousand hand-checked extractions used to test the tool and to tune it. Eighteen months on, the volunteers check the tool’s output rather than typing from scratch, the model file has not changed once, and the clinic can answer the question of where its clients’ documents go with a single sentence.
Worth arguing about
The team prototyped on the closed API and shipped on open weights. What did the prototype buy them that the architecture decision itself did not?
One answer
It told them what the task actually was. Two weeks of cheap, immediate iteration turned a vague brief (summarise case files) into a narrow, checkable one: extract seven fields from a document that is in front of the model. That reframing changed which architecture could do the job, because the open model’s weakness is memory of facts and the extraction task requires none. Deciding the architecture first would have been deciding it against the wrong requirement.
Name three things the open-weights route gave the clinic that no clause in an API contract could.
One answer
First, the documents never leave the building, which is a physical fact rather than a promise that can be overridden by a legal process elsewhere. Second, the model cannot change under them: the file downloaded is the file that runs next year, so a tested behaviour stays tested. Third, there is no per-document price and no dependence on a connection, which for a clinic on an uncertain grant and an uncertain line is the difference between a tool and a subscription.
Most of the budget went on scanning and hand-checked examples rather than on the model. Why is that the usual shape of such a project?
One answer
The model is the cheap part and has been getting cheaper by roughly an order of magnitude a year for a fixed level of capability; what is expensive is assembling and labelling examples of your own situation, because nobody else has them and they cannot be downloaded. The same pattern appears in every field deployment in this course: the vision system’s cost is mounting the camera and labelling the parts, not the network. It is also what makes the result defensible, because the hand-checked set is the only evidence that the tool works on this clinic’s documents.
Test yourself6 questions on this module
The method for training multi-layer networks was popularised in 1986, in the middle of the second AI winter, and mattered little for twenty-five years. What changed?
Why did a chip designed to draw video-game frames turn out to be the right machine for training networks?
What property of the 2017 transformer mattered most for the years that followed?
A lab reports that its model’s final training run cost 5.6 million dollars. What does that figure leave out?
Why do the labs expect the stock of public human-written text to become a binding constraint within a few years?
A lab describes its new model as open. What does that almost always mean in practice?
Beyond text: pictures, voices and video
9 lessons · 1 h 19
You will be able toExplain how a diffusion model turns a prompt into an image and why negation in a prompt fails, account for the early failures at hands and lettering from the training data and the text encoder, describe what a vision model sees when it reads a photograph and where it is reliably blind, explain why a voice can be cloned from seconds of audio while video stays inconsistent across time, and state what a sampling-time watermark can and cannot survive.
- 6.1A picture, out of noise
- 6.2How words steer the picture
- 6.3Why the hands were wrong
- 6.4When the model looks at a picture
- 6.5A voice from three seconds
- 6.6Music from a prompt
- 6.7Why video is so much harder than a still
- 6.9One model, many senses
An illustrative case, built from documented patternsThe doctor’s voice
The film had to play at two hundred and forty anganwadi centres and travel on WhatsApp, which meant short, in Marathi, and recognisable. The unit’s three previous campaigns had been narrated by Dr Kulkarni, a retired district health officer whose voice is known across the region from a decade of radio spots. In February he had a stroke and can no longer record.
A production vendor came with two offers.
The first was the voice. Forty seconds of an old radio spot was enough, the vendor said, to build a clone that would read any script the unit wrote, in Marathi, for nine thousand rupees. He demonstrated it on a phone in the meeting and the unit’s own staff could not tell.
The second was the pictures. Instead of a shoot at one lakh forty thousand (a day’s crew, a village street, a mother, a health worker, permissions) the vendor would generate the footage from a description. He showed samples: a lane in the rain, a clinic doorway, hands holding a vial.
The hands were wrong in three of the five clips. In one, the vial had no cap and then had one. The unit’s programme officer, who had spent nine years in those villages, said something more useful about the lane: it was not from here. The doors were wrong, the drainage was wrong, and the way the water sat on the road was wrong. She could not have specified it in advance and she recognised it instantly, which is exactly the failure that costs a health film its credibility with the audience it is for.
The voice was the harder question, because the voice worked.
Dr Kulkarni’s son said his father would have wanted the campaign to go out and offered his consent on his father’s behalf. The unit’s medical officer said, correctly, that a man who cannot now speak cannot consent to being made to speak, and that the reason the voice was worth using was precisely the reason it should not be synthesised: people in those villages would believe the film because they believed him.
Against that sat the drive. Two hundred and forty centres, a monsoon window that closes, and a budget that could not absorb both a studio narrator nobody knows and a location shoot. And the unit knew what happens to a health message that nobody trusts, because it had spent the previous year undoing a WhatsApp forward about the same vaccine.
The forward was the reason the labelling question came up at all. It had carried a photograph of a child, and when the unit tried to establish where the photograph came from it found the image on a stock site, taken in another country, eleven years old. Nobody had generated anything. The most common fake in the district was a real picture with a false caption, and a reverse image search had settled it in thirty seconds.
That left the unit with an awkward asymmetry it discussed for most of an afternoon. If it labels its own two generated shots, it has told the truth about a film nobody was going to doubt. It has not made the forwards any easier to check, because a forward carries no label and absence of a label means nothing. What it has done is establish its own practice, in public, before anybody asks, which the district information officer argued was the only kind of credibility that survives an argument.
How it played out
They did not clone. Dr Kulkarni’s son recorded the narration in his own voice and opened the film by saying who he was and that he was reading his father’s words. In the review screenings the anganwadi workers preferred it: the introduction, not the timbre, turned out to be what carried the trust, and several said so unprompted. The unit shot the street, the doorway and the health worker on a phone in one afternoon for about eleven thousand rupees, using a real centre and a real worker who was paid for the day. Generated footage was used for two five-second establishing shots, of clouds and an empty road, where nothing had to be right and nobody had to be recognisable. The end card carried a line naming those two shots as generated. The vendor’s voice quote was refused in writing, and the unit adopted a one-page rule that it has applied since: no voice or face of an identifiable person is ever generated, and anything generated is labelled on the film.
Worth arguing about
Forty seconds of an old radio spot was enough. What does the model actually learn from those seconds, and why does the length matter so little?
One answer
It does not learn the voice. It has already been trained on thousands of speakers to separate who is speaking from what is said, and the speaker is represented as a short list of numbers: a position in a space it learned from everybody else. The forty seconds are used to locate Dr Kulkarni’s voice in that space, after which any sentence can be generated from that position. Locating a point needs far less evidence than learning a space, which is why a few seconds suffices and why longer samples add little.
The generated hands failed and the generated street looked wrong to a local. Those are two different failures. Name the mechanism behind each.
One answer
The hands are a data problem: hands appear small, partly hidden and in thousands of poses in training photographs, so what the model learned is a texture of finger-like protrusions in an unspecified number rather than an object with five of them. The street is a different failure: the model produces the likeliest street given the words, which is the median of everything it has seen captioned that way, so it lacks the specific local detail nobody thought to put in the prompt. One is thin support for a rare structure; the other is the median supplied where the particular was needed.
The end card labelled the two generated shots. What can a label like that achieve, and what can it not?
One answer
It can establish the unit’s own practice and make its choices auditable by the people it serves, which is a positive claim about provenance from a source with something to lose. It cannot survive the journey: a WhatsApp re-encode, a crop or a screenshot strips embedded marks and an end card is simply cut off. And it says nothing about any other film, because absence of a label is not evidence of anything when most material carries none.
Test yourself6 questions on this module
What was an image model trained to do?
Why does a prompt reading ‘a street with no elephants’ tend to produce elephants?
Generated hands were wrong for about eighteen months and then largely stopped being wrong. What fixed them?
Which question about a photograph is a vision model least likely to answer correctly?
Why is three seconds of audio enough to clone a voice?
A platform’s detector finds no watermark in an image. What follows?
Putting it to work without getting burned
10 lessons · 1 h 31
You will be able toChoose a task a model is reliably good at and one it is not and explain the difference from its mechanism; state where a typed conversation goes and how to stop it being used for training; run a small open model on your own hardware; estimate the cost and energy of a query to within an order of magnitude; and explain why an agent that acts on your behalf fails differently from a chatbot that only answers.
- 7.1The shape of a task it is good at
- 7.2Give it the material, not the question
- 7.3Where your words go
- 7.4Free tiers, and what they quietly ration
- 7.5A model on your own laptop or phone
- 7.6What a query costs, in rupees and watt-hours
- 7.7The assistant inside your email and spreadsheet
- 7.8When it starts to act
- 7.9What not to hand it
- 7.10Keeping your own judgement
An illustrative case, built from documented patternsThe clause and the 48-hour deadline
The revised supply agreement arrived at nine in the evening on a Friday, with a request for signature within forty-eight hours. Thirty-four pages of English. Meena’s advocate was at a wedding in Erode until Monday afternoon.
Clause 19 was new and it was an indemnity. She could read the words and could not tell what they obliged her to do if a shipment was rejected at the port.
Her first instinct was the obvious one: paste the whole PDF into a free chatbot and ask what had changed since the last version. It would take ninety seconds.
Two things stopped her, and neither was squeamishness. The agreement itself contains a confidentiality clause covering its terms, and pasting it into a free consumer tier means disclosing it to a third party under terms that, by default, permit the text to be used in training the next model. Whatever the practical risk, she would have done the thing the document forbids, on the same evening she was being asked to sign it.
She tried a version of it anyway, on a general question about indemnities, and got something useful. Then she asked what the penalty cap was, and got a figure (a number, a currency, a clause reference) that is not in the agreement. She only noticed because she had the page open. The figure had the right shape and no source.
She tried again, differently. She asked it to explain what an indemnity clause generally obliges a supplier to do, without pasting anything at all, and got a clear, useful, checkable explanation of a concept that is written about in ten thousand places. That answer was worth having and she could have got it from any textbook; the difference was that she got it at nine forty on a Friday.
The distinction between those two questions is the whole of this case. What is an indemnity is dense in the material the model was trained on, general, and cheap to verify. What does clause 19 of this agreement cap my liability at is specific, private, appears nowhere in any training text, and is exactly the kind of thing that comes back as a number with the right shape and no source.
Her brother, working on the same problem in the next room and not talking to her about it, had by then pasted the entire agreement into a different free tool. He had also, without thinking about it, accepted the tool’s default terms four months earlier when he signed up to draft a marketing email.
The cost on both sides was real. Sign without understanding clause 19 and she is exposed on the one relationship the business cannot lose. Miss the deadline and she risks the relationship anyway, in a season when the buyer has alternatives in three countries. Wait for Monday and she has six hours, not forty-eight.
There was also a quieter cost that she named to her brother the following week. Twenty-two people’s wages depend on this buyer. A tool that produces a fluent, confident, well-formatted answer at ten at night to a person who is tired and frightened of a deadline is at its most persuasive exactly when it should be at its least trusted, and no amount of knowing that changes how it feels in the moment. She had believed the invented penalty figure for about forty seconds, and the only reason she stopped believing it was that the agreement happened to be open on the other screen.
How it played out
She did three things, in about twenty minutes. She opened the account’s data controls, turned off the setting that permits training on her conversations, and switched to the temporary-chat mode, both of which she found by looking, and neither of which she had known existed. She replaced the buyer’s name, the addresses and every price with BUYER and AMOUNT using find-and-replace, because none of them are needed to explain what an indemnity obliges. And instead of pasting thirty-four pages she pasted two: the new clause 19 and the old clause 19, and asked what the difference required her to do if a shipment was rejected. That answer was checkable against the two paragraphs in front of her in two minutes, and it was right. She then asked for a list of questions to put to her advocate rather than for advice, sent those on Sunday night, and asked the buyer for a seventy-two-hour extension in a message that quoted the clause and named the specific ambiguity. The extension was granted within an hour, because the message showed she had read the document. The business now has a policy pinned above the desk, one line long: nothing with a name, a price or a customer in it goes into a chat window.
Worth arguing about
Two of Meena’s three changes were about where her words went and one was about accuracy. Which was which, and why did the accuracy one work?
One answer
Turning off training with temporary mode, and stripping names and prices, were both about disclosure. Pasting the two versions of clause 19 instead of the whole agreement was the accuracy change. It worked because it moved the task from the model’s memory to the material on the desk: the answer to what changed between two paragraphs is contained in the two paragraphs, so the model is reading rather than recalling, and the result is cheap to check against the same two paragraphs.
The chatbot produced a penalty cap that is not in the agreement. Why is a specific figure the most likely kind of thing to be invented?
One answer
Invention concentrates on specific details inside familiar structures. The model has read a great many contracts and knows the shape of a penalty cap (a number, a currency, a clause reference) so producing one requires no knowledge of this agreement at all. Where training support is dense the likeliest continuation is true; where it is thin, as it is for one clause of one private contract, the likeliest continuation is merely plausible, and the tone is identical either way.
Her brother pasted the whole agreement into a different free tool. Name what was disclosed, to whom, and what a consumer free tier’s defaults typically do with it.
One answer
The buyer’s confidential terms, prices and identity were disclosed to the tool’s provider, which is a third party the buyer never agreed to. On a consumer free tier the text is stored, may be sampled and read by a person for quality and safety review, and by default may be included in the material used to train a future model, the last of which is effectively irreversible and cannot be undone by deleting the conversation. Deletion is also a promise by a company, which a legal process elsewhere can override.
Test yourself6 questions on this module
Which of these tasks sits on the reliable side of the mechanism?
You must discuss a client’s file with a chatbot and have no access to an employer’s paid tier. Which action helps most?
An eight-billion-parameter model is about sixteen gigabytes at sixteen bits per number and under five at four bits. What has been traded away?
An agent is right on 95 per cent of its individual steps. Roughly how often does it complete a twenty-step task correctly?
Turkish secondary students given a chatbot that supplied answers solved more practice problems and scored seventeen per cent worse on the exam; a group given a hint-only version matched the control. What is the mechanism?
Why is ‘use it to prepare, never to decide’ the right rule for a medical or legal question?
AI and work, with the evidence
11 lessons · 1 h 40
You will be able toDistinguish a task from a job when reading a claim about automation, quote the size of the productivity effect the controlled studies actually found and for whom, explain from the elasticity of demand why automating a task can grow or shrink an occupation, say why entry-level roles are exposed before senior ones and what that does to a trade’s training ladder, and describe the human labour a trained model depends on that its price does not show.
- 8.1AI and jobs, without panic or dismissal
- 8.2Measuring exposure, and what the numbers do not say
- 8.3What the controlled experiments found
- 8.4The study where it made experts slower
- 8.5Novices gain first, and what that means for everyone else
- 8.6The rung that goes missing
- 8.7What the cash machine did to bank tellers
- 8.8The first place it showed up in pay
- 8.9The labour that trained it
- 8.10Six trades, as they stood in 2025
- 8.11What an early-career person can actually do
An illustrative case, built from documented patternsThe intake decision
For eleven years the firm has hired about a hundred and twenty engineering graduates every June. In the January planning meeting the delivery head proposed thirty.
His case was not speculative and he had numbers. Three of the firm’s four largest accounts had asked for lower rates at renewal. The coding assistant, in use for fourteen months, was drafting a large share of the routine work. And the firm had run its own small measurement, which is more than most firms do: on well-specified tickets in a common framework, the least experienced engineers were meaningfully faster with the tool. A graduate costs about six point two lakh fully loaded in the first year and bills nothing for roughly five months.
The same measurement had produced a second result that the delivery head reported honestly. On the legacy insurance codebase (nine hundred thousand lines, fifteen years old, three people who understand why the reconciliation module is written the way it is) the firm’s two most senior engineers were slower with the assistant than without it. They read plausible suggestions, decided they were wrong, and wrote their own. Both had told the delivery head, before the measurement, that the tool was helping them.
The HR head’s case was structural. All twelve of the firm’s current team leads came through this intake. Nobody in the room could describe another route by which the firm makes a person who can look at an account manager and say no. And the accounts that pay the best rates pay them for exactly that person.
She also mentioned the 2025 payroll study showing employment for twenty-two to twenty-five year olds falling in the most exposed occupations while their older colleagues held steady. The delivery head said, accurately, that it is one study, in one country, in years that also had a hiring correction and rising interest rates. Both of them were right, which is what made the meeting hard.
A third voice in the meeting was the account director for the insurance client, who made a point neither side had. The firm does not sell code. It sells somebody who will be answerable at half past eleven at night when a reconciliation run fails during a month-end close. That answerability is what the rate is for, it cannot be produced by a tool that cannot be sacked, and it is currently produced by a process that starts with a graduate fixing small bugs badly.
The delivery head accepted the point and returned a harder one. The rung is not disappearing because the firm chooses to remove it. It is disappearing because the work on that rung has stopped being worth what a client will pay for it, and no amount of internal conviction changes a rate card. If the firm wants juniors, it has to find something for them to do that a client will still pay for, or pay for their training out of its own margin and say so.
The arithmetic on the table: cutting to thirty saves about five point six crore over two years, against a risk that cannot be priced: that in 2032 the firm buys its team leads at a premium from firms that kept making them. Nobody in the room had lived through this before, and both of the people arguing said so.
How it played out
They cut to seventy and changed the job rather than only the number. A junior’s first six months became review work: reading the assistant’s output against the ticket and the account’s own conventions, finding what was wrong, and writing up why, with a team lead signing off. Two things came out of it that nobody had predicted. Juniors reached billable work about seven weeks earlier than the previous cohort, because reviewing exposes the account’s conventions faster than writing boilerplate did. And the leads reported that the people who were good at finding the tool’s errors were substantially not the same people who had topped the firm’s coding test, which changed how the firm recruits. The write-ups were kept in one place, and after eight months that log (every situation in which the assistant was confidently wrong on their own codebases) was the most valuable internal document the firm had, because it is a map of the frontier for their work that no vendor could supply. The delivery head’s note recorded the open question honestly: whether checking without ever having produced builds the judgement that producing used to, and that nobody yet knows.
Worth arguing about
The same tool made juniors faster and two senior engineers slower, in the same firm, in the same month. Explain both from one mechanism.
One answer
A model supplies the median of competent practice from its training. A junior sits below that median, so the suggestion raises their output and saves them time. The seniors on the legacy codebase sit far above it, and the knowledge the task needed (why the reconciliation module is written that way) is not in the code and was never in the model. For them a fluent suggestion is something to read and reject, which costs more time than writing the right answer they already knew.
The firm cut intake by more than a third and called it a change to the job. What ladder risk did that not remove?
One answer
Forty per cent fewer people are entering the pipeline at all, so even if review work builds judgement as well as production did, the firm is making fewer seniors than it used to. And the mechanism itself is unproven: the closest evidence, from the schools study where students given answers scored worse on the exam and students given hints did not, suggests that the difference between supervising and doing is exactly what determines whether the skill forms. The firm has made a reasonable bet and it is a bet.
Why was the firm’s log of the assistant’s errors more valuable to it than any vendor benchmark?
One answer
A benchmark measures a public test that the model may have seen, on tasks that are not the firm’s. The log records where the jagged frontier runs for this firm’s codebases, conventions and clients, which is unknowable from outside and changes when the model or the codebase does. It is also the only asset in the firm that improves with use of the tool rather than being made obsolete by it, and it is what lets the firm tell a real regression from three unlucky runs.
Test yourself6 questions on this module
A study reports that an occupation is 60 per cent exposed. What has actually been measured?
Across four 2023 experiments the least experienced workers gained most and the most experienced gained least. Why?
Sixteen expert developers were 19 per cent slower with AI tools and believed they had been 20 per cent faster. Which conclusion does that support?
Which question decides whether automating a task grows or shrinks the occupation around it?
Why did the effect on pay and work show first, and most sharply, on freelance platforms?
What is the specific mechanism that the entry-rung argument says is breaking?
Who controls it, and what is unsettled
10 lessons · 1 h 37
You will be able toName who controls each layer of the stack and where the chokepoints are; state what the EU AI Act and the current Indian, British, American and Chinese positions require of a chatbot and of a high-risk system; lay out the copyright and authorship disputes as disagreements between named positions without resolving them; put a figure on the electricity a data centre draws and say what the per-query number leaves out; explain from the mechanism why a refusal can be trained but not guaranteed; and read a claim about AI with the questions that separate a demonstration from a deployment.
- 9.1Four layers and their chokepoints
- 9.2The laws that have arrived
- 9.3The copyright fight, as a fight
- 9.4Who owns what it makes
- 9.5The electricity and the water
- 9.6The safety argument, both sides fairly
- 9.7Why a refusal can be trained but not guaranteed
- 9.8What “AGI” means, to whom
- 9.9Questions nobody has answered yet
- 9.10How to read the next headline
An illustrative case, built from documented patternsThe data centre and the borewell
The proposal was for forty acres, a phased build to about three hundred and fifty megawatts, and an investment figure of eight thousand crore rupees. The council had been told four thousand jobs. The figure in the developer’s own annexure was four thousand during construction and about a hundred and eighty permanent, which two councillors found on page sixty-one the night before the vote.
The two asks were specific. A grid connection larger than the town’s entire current draw, which the state utility would build. And a water allocation for cooling, from a municipal supply that had run on tankers for nine weeks the previous summer.
The cooling turned out to be the one genuine lever the council held. A site can be cooled evaporatively, which uses a great deal of water and less electricity, or with closed-loop chillers, which use very little water and more electricity and cost more to run. It is a choice made per site, and it is not a technical choice in a district on tankers. The developer’s engineer was straightforward about it: closed loop would raise operating cost, and the cost would be passed to tenants.
A councillor asked what the computers would be doing. Nobody could say. The developer explained, honestly, that it does not know either: tenants rent the capacity and decide what runs on it, and the mix between AI training, AI serving and ordinary hosting changes weekly. That answer landed badly and was correct.
A second fact was raised by the district’s own environment cell. The state’s grid is around seventy per cent coal, so the same computation carries several times the carbon here that it would in a hydro-rich region. That is not something the council can regulate. It is something the developer’s customers increasingly ask about, which made it a lever of a different kind.
Against refusal sat the ordinary calculus of every such vote. Two neighbouring districts were competing for the same investment and one of them would say yes. The substation and the road would be built either way only if the project came here. And a hundred and eighty permanent jobs is not four thousand, but in that town it is not nothing.
The council also had to decide what it was competent to decide. A councillor proposed a condition that the site not be used for artificial intelligence. The municipal solicitor advised against it in three sentences: the council has no power to regulate what a lawful tenant computes, no means of inspecting it, and no definition of the term that would survive a challenge. The condition would be unenforceable, and an unenforceable condition is worse than none, because it lets everybody claim the matter was dealt with.
What the council could regulate was a pipe, a meter and a land classification. That felt small in a debate about a technology and it was the only part of the debate the council was actually holding. The state utility would decide the grid connection. The chips would be bought under rules written in Washington and manufactured on an island the council had no view on. The tenants would be signed in another country.
One councillor put it plainly in the minute she asked to have recorded: we are not voting on artificial intelligence, we are voting on forty acres and a borewell, and the only honest thing we can do is get those two right.
How it played out
The council approved, with two conditions and one refusal. It required closed-loop cooling with a metered water cap, the meter reading published monthly on the council’s noticeboard and website. It required a written commitment that during any declared scarcity period the site would take no municipal water at all and would meet its need from tankered or recycled supply at its own cost. And it refused to convert the land at agricultural rates, which added materially to the developer’s cost and passed some of the value back to the town. It did not attempt to regulate what the computers did, having been advised, correctly, that it had no power to do so and no way to verify anything it required. Two years on, the monthly meter is the number residents actually read, and the developer’s own tenants cite it in their reporting, which has turned a condition into a selling point. Three councillors still believe the jobs figure was oversold. It was.
Worth arguing about
The council could act on the water and not on what the computers did. Locate that boundary in the four layers of the stack.
One answer
The council sits at the buildings layer, and the buildings layer is physical, local and licensable (land, water, a grid connection) which is exactly what a municipal body can attach conditions to. Everything above it, the tenants and the models they run, is decided elsewhere and moves weekly, and everything below it, the chips and the machines that make them, is controlled by a handful of firms and two or three governments. That is the general shape: local authorities can regulate the site, not the computation.
A developer can publish a carbon figure of zero and a figure of eleven thousand tonnes for the same year. How, and which one does the grid see?
One answer
The larger figure is location-based: what the grid actually emitted to supply that electricity, which in a seventy-per-cent-coal state is substantial. The zero is market-based, computed after applying renewable-energy certificates bought elsewhere. Both are legitimate accounting conventions and both appear in company reports, sometimes in the same table. The grid, and the air, see the location-based number, so the honest question when reading any such claim is which of the two is being quoted.
The council required a published monthly meter rather than a one-off commitment. Why does that suit this particular harm?
One answer
The harm is cumulative and local rather than a single event, so a promise made once cannot be tested and a breach would be invisible. A monthly published figure converts an unverifiable commitment into an ongoing measurement that residents, journalists and the developer’s own customers can read, which is the same principle as keeping a personal test set: what nobody measures stops being true. It also costs almost nothing to comply with if the commitment was genuine.
Test yourself6 questions on this module
Why can two or three governments effectively decide who is able to train a frontier model?
Every AI regime in force by 2025 shares one limit. What is it?
Two US judges found training on lawfully obtained books to be fair use in June 2025, and one of the labs still paid about 1.5 billion dollars. Over what?
You generate a logo from a detailed prompt and use it unedited for your business. In the United States, what is the likely position?
A lab reports the training of one model at both zero tonnes of carbon dioxide and about eleven thousand tonnes, in the same report. How can both appear?
Why does every jailbreak work for a while and then stop working?
What this course is
You have heard that AI matters. Nobody has told you what it is. This course starts from nothing: no maths, no code, no assumed background. By the end you will know what the word actually names, how a trained model differs from a program someone wrote, what a chatbot is doing when it answers you, why it can be badly wrong while sounding certain, where this technology already sits in your day without a label on it, what changed around 2022, and how to think about AI and work without either panic or dismissal.
Who wrote it
Founder and series editor: Dr Mustafa Mun. Written by AI models to a written standard. Exam keys checked blind by a second model: 3,665 of 3,666 agreed. Academic review invited.
More in Start here
- AI, Safety and What Goes WrongThe failure modes of AI, stated plainly, with the numbers.
- Machine Learning, FoundationsThe classical ground under modern AI, for someone who can read code.
- Getting Real Work out of a ModelYou already use ChatGPT, Claude or Gemini. This is how to stop getting average answers.
- How a Language Model Actually WorksThe machinery under the chat box, explained without matrices.
