From the dream of thinking machines to AI that writes. Nearly 400 years of challenges, to touch, run and check for yourself
We went back to the original sources on AI, such as papers, books and articles from the time, and opened 667 of them one by one. Then we implemented how the ideas work in 146 programs.
Behind the one line in a textbook lies a real story that is thrilling. For the famous stories, we went back to the speaker's own book, paper or article from the time and checked. You can check how things work with your own hands: move the figures and run Python. Start from any chapter.
01Chapter 01 · Overview
Waves of Booms and How They Got Numbered
Who numbered the “first to fourth AI booms”, and when?
AI has gone through periods of rising hopes (booms) and falling hopes (winters) many times. But the size of a boom cannot be seen. So this site counted, year by year, how often certain words were used in English books, in the titles of papers worldwide and of Japanese books, and in remarks in Japan's National Diet, and looked at the shape of the waves.
The figure on the right shows that real data. Diet remarks that use “AI” to mean AI formed a peak in 2019, dropped, and in 2023 rose above the earlier peak. But the shape changes with how you count. Searching for the two letters “AI” also catches words likeAIDSandAIG. So we looked at the hits one by one, made a standard, and counted again.
The numbering “first to fourth” is the way of counting commonly used in Japan. In English books, it is not the booms but the that gets numbered. In the Diet in 1985, it was explained as (translated).
What you think you knowThe popular story:The was a term Minsky and Schank warned of The original source says:In the record of the 1984 panel, Minsky is not among the panelists. The words appeared as the name of the worst outcome that might be coming.
Sources & confidence (3)Waves of Booms and How They Got Numbered
4 April 1985Verified in the originalSources disagreeJapan
In the 1985 Diet, AI is explained as being said to be (translated)
Takemochi Ishii of the University of Tokyo was called to the Diet (a committee of the House of Representatives) and explained, (translated). He said the first was an effort centered on the United States from the mid to late 1960s, and the second was Japan's Fifth Generation Computer project. The idea of counting booms was already around in the middle of the second boom.
What we still don’t know:We do not know who started the phrase (translated) before 1985 (this is the oldest instance found within the Diet records).
2 sources and how they were checked
Where sources disagree:Ishii gives the period of the first boom as “the mid to late 1960s.” Many Japanese sources of the 2010s say “the late 1950s to the 1960s” (such as the 2016 White Paper of the Ministry of Internal Affairs and Communications; see another row)
1984: was spoken of as the name of the worst thing that might come
At a panel discussion at AAAI-84, the moderator, Drew McDermott, said that researchers were worried that expectations for AI were too high and that it would someday end in trouble. As the worst-case scenario he gave this picture: in five years the strategic computing initiative fails miserably, Japan's Fifth Generation also does not work out, the Japanese government quickly pulls out of computers, the start-up companies all go bankrupt, and no money goes to anything related to AI. He described this as . He urged them to warn themselves so that it would not come to that, and to tell the world. In other words, “The AI Winter” was a phrase that appeared in the middle of the second boom as a warning about the future. Calling the decline in research funding in the 1970s the is a label added afterward.
The popular story:It is often thought that the drop in research funding in the 1970s was called an at the time The original source says:The oldest record found is a 1984 discussion, where it appears as the name of the worst thing that might come in the future (the speaker said ). The (the 1970s) is a label added afterward. English-language books number the winters, as in , but is hardly used
What we still don’t know:Who first said is not known (even in the discussion it was “by some”). What book the small value for 1983 in the Ngram comes from has not been confirmed.
2 sources and how they were checked
The Dark Ages of AI: A Panel Discussion at AAAI-84 (Drew McDermott, M. Mitchell Waldrop, Roger Schank, B. Chandrasekaran, John McDermott · 1985 · p.122 Drew McDermott's opening remarks · Original source)
Calling booms by number, “first, second … boom”, is mostly a Japanese way of counting (English numbers the )
Word frequencies in English-language books (Google Books Ngram) show that appears from 1983 and rose sharply in the late 2010s. Expressions that put numbers on winters, such as and “second AI winter”, also exist. On the other hand, , and did not appear in countable amounts. In Japanese, “first artificial intelligence boom” (translated) can be seen in a 1982 magazine, (translated) in a 1985 book, and (translated) in the Diet in 1985. From 2014, the first, second and third AI booms were used in an academic society journal, and they also appear in a chapter title of a 2015 book by Yutaka Matsuo and in government white papers from 2016 on.
The popular story:People tend to think “first to fourth AI booms” is a worldwide way of counting The original source says:Numbered “booms” are mostly a Japanese expression. English-language books put numbers on the winters (“The AI Winter”: first/second AI winter) and do not number booms. The U.S. DARPA uses a different way of counting,
What we still don’t know:We have not looked at how this is counted in Chinese (such as phrases for a “third wave” of AI) or Korean. Ngram covers only books through 2022, so we do not know the English expressions from 2023 onward.
What the figure shows:The shape and size of a boom change with the way it is counted. Numbering booms from 1 to 4 is mainly a Japanese practice; English accounts tend to number the winters instead.
02Chapter 02 · Up to 1955
Thinking Machines, Computing Machines
Since when has been asked in earnest?
In 1637, Descartes described two ways to tell a human-like machine from a real person. The “chess-playing machine” of 1770 had a person hidden inside. In 1843, Ada Lovelace wrote notes on the Analytical Engine. In Edo-period Japan, mechanical karakuri dolls were built.
In 1936, Alan Turing presented the idea of a machine that computes with just a tape and a table of rules. Open the lid of the 1936 box in the figure on the right to see that machine adding 1 to a binary number. The head reads a symbol on the tape, looks it up in the table, rewrites it, and moves one step left or right. He argued that any computation can be written as a combination of these simple moves.
In 1943, Warren McCulloch and Walter Pitts described the brain's nerve cells (neurons) as switches. A neuron adds up its inputs and fires once the total reaches or exceeds a set value. This is the starting point of neural networks. Then in 1950, Turing replaced the question with an imitation game.
What you think you knowThe popular story:Pass if you fool 30% of the judges The original source says:That standard is not in Turing's paper. What he wrote was a forecast about 50 years ahead.
Turing, : defining what it means to be with a machine in the head
Alan Turing published the paper . He simplified the steps of a person calculating with paper and pencil down to a that has a tape divided into squares (in place of paper), a head that reads and writes one square at a time, and only a finite number of states (Sections 1 and 9). He defined a number whose decimal digits this machine can write out as . He further showed that one machine (a universal machine) can compute any computable sequence if it receives the description of another machine on its tape (Section 6). And he showed that there is no method that always decides, by a fixed procedure, whether a logical formula can be proved (the answer to the decision problem) (Section 11). The next year this model was named the , and it is regarded as a foundational model of the theory of computation and of computer science.
The popular story:People tend to take it that “Turing designed the computer (the Turing machine) in 1936” The original source says:The machine in the paper is a model in the head, a simplification of the steps of a person calculating with paper and pencil (Sections 1 and 9). The “computer” in the paper means a human who calculates, and on page 250 it is written as he. The name is not in the paper either; his own names were automatic machine and the like. It was Church’s review the next year that named it (SEP).
9 sources and how they were checked
Where sources disagree:Year: the received date on the printed page is May 28, 1936 and the date it was read to the society is November 12, 1936. The year of the volume it appeared in (Vol. 42) is 1937 in the publisher’s registration (Crossref) and in the King's College catalog, and SEP gives “1936–7”. This site gives both: “1936 (received and presented), journal volume 1936–37”.
The McCulloch and Pitts paper: writing the brain’s nerve cells as a circuit of switches that fire or do not fire, in formulas
Warren McCulloch and Walter Pitts published the paper . Because the activity of a nerve cell (neuron) is (it fires or it does not), they reasoned that the workings of a neural network can be described by propositional logic (logic with only two values, true and false). As premises for the calculation they set that firing is all-or-none, that a neuron fires when a certain number of synapses are stimulated at the same time, that if even one inhibitory synapse is active the neuron does not fire, and that the structure of the network does not change with time (page 118). They further wrote that if a tape and a reading device are added, this network can compute the same numbers as a Turing machine (page 129). It is regarded as a starting point of later research on artificial neurons.
The popular story:(1) General explanations often introduce it in the order “McCulloch and Pitts in 1943 = a model of nerves; Hebb in 1949 = a mechanism for learning” (for example, page 2 of the Nobel Prize explainer) The original source says:The 1943 paper also deals with learning. Taking the formation of new synapses as the simplest kind of change, it assumes that when the neuron fires and the endings are excited at the same time (), the endings become ordinary synapses, and it writes that such a change can be replaced by a network with loops (Theorem VII) (page 124). However, as a premise for the calculation, it sets that the structure of the network does not change (page 118). (2) Some summaries write that the paper (Nilsson, page 34) → On page 129 of the paper, it says that with a tape and a reading device the network can compute the same numbers as a Turing machine, and that a network without a tape can compute only some of them.
What we still don’t know:The paper itself cautions that the , that a learning network can be replaced by a network whose structure does not change, is not an explanation of facts about the real brain (page 117). That real neurons do not work exactly as these premises assume (all-or-none, unchanging structure) can be used as an example for understanding the difference between a model and the real thing.
Turing publishes a paper discussing machine intelligence through the
The British mathematician Alan Turing published a paper that replaces the question with the . The original is a game in which an interrogator tries to guess, using only written exchanges, which of a man and a woman in another room is which. Turing turned it into the question of how often the interrogator would be wrong if a machine played the man’s part. The paper also discusses answers to 9 objections and the idea of a that is raised by education.
The popular story:It tends to be called the The original source says:In the paper it is called the , and the term does not appear in the body of the paper. Also, the paper tends to be thought of as an answer to → he himself wrote that this question is (page 442 of the printed pages) and replaced it with a different question using the game.
What we still don’t know:We have not confirmed on this site who first used the name , or when.
Kempelen, a nobleman from Pressburg in Hungary, built a machine at the court in Vienna for Empress Maria Theresa: a figure in Turkish dress that played chess on top of a cabinet. It toured Europe and America and amazed many people, but in fact a skilled chess player was hidden in the cabinet and moved it. As early as 1784 a book was published saying that a person was hidden inside and playing, and in 1821 a book appeared that explained with diagrams how the person hid. The machine was destroyed in a fire in Philadelphia in 1854.
The popular story:People tend to say “in the 18th century there was a thinking machine that played chess” The original source says:In fact a person was hidden in the cabinet and operated it. According to the book (1784) by Kempelen’s contemporary friend Windisch, Kempelen began the work by hinting to the Empress at the idea of , and he called the device . Poe (1836) also quotes him as saying that it was a , and that it looked wonderful because of the boldness of the idea and his skill in choosing the way to create the illusion.
6 sources and how they were checked
Where sources disagree:Year of construction: there is a 1769 account (the HNF museum says “he showed it to the Empress in 1769”, and Poe 1836 says “invented in 1769”) and a 1770 account (Linda Hall Library). Windisch (1784) writes “he promised it in 1769 and finished it in 6 months”. Place of the fire: HNF says the “Chinese Museum” and the Linda Hall Library says “Peale’s Museum” (both in Philadelphia, 1854). Timing of the exposure: it came in stages, with Thicknesse’s claim in 1784, the book of analysis in 1821 and Poe in 1836. The story that the owner’s son Mitchell revealed everything in a magazine in 1857 could not be checked here because we could not open the original magazine (Google Books had hit its search limit, and HathiTrust would not let us view it). Its only basis is Wikipedia, so it is unconfirmed.
What the figure shows:The question “Can machines think?” did not suddenly appear in 1950: for over 300 years after Descartes wrote in 1637 about ways to tell human-like machines from people, people built and imagined machines that seemed to think, using dolls, gears, cards, tapes, and switches, but inside were hidden people or fixed procedures such as tables, gears, cards, rule tables, and switches. In 1950, Turing stopped asking about their inner workings and proposed the imitation game: could a machine be identified through written exchanges alone?
03Chapter 03 · 1955–1960
Gets Its Name
A machine that corrects itself when it errs: what did it learn?
In 1955, the proposal for a summer workshop used the name . What the proposal held was not a plan to finish the job in one summer but an expectation that significant progress could be made on one or more problems.
In 1958, the US Navy showed Frank Rosenblatt's perceptron to reporters. After about 50 trials, it could tell whether a mark on a card was on the right or the left. Try showing it cards in the figure on the right. Only when it errs does it correct the weights of the squares where the mark was. Look at the weight pattern at the end, and you can see that the machine knows no words like “right” or “left”; it only learned which squares vote for which side.
Around the same time, Herbert Simon and Allen Newell made predictions such as “a digital computer will be the world's chess champion within 10 years” (translated), and even wrote down the day the answers would be checked.
What you think you knowThe popular story:The Dartmouth people meant to finish AI in a single summer The original source says:What the proposal held was an expectation of significant progress on one or more problems.
31 August 1955Verified in the originalSources disagree
The proposal for a summer workshop that put forward the name
Four people, McCarthy, Minsky, Rochester and Shannon, drew up a proposal to hold a workshop on at Dartmouth College the following summer, and asked the Rockefeller Foundation for funding. The proposal started from the conjecture that every aspect of learning, and any other feature of intelligence, can in principle be . It lists research topics such as the use of language by machines, the forming of concepts, and self-improvement. The amount requested was $13,500 in total.
The popular story:People tend to say “they meant to complete AI in a single summer” The original source says:The proposal only says that if a carefully selected group of scientists worked on it together for a summer, on the list. It does not say they would complete it (proposal p. 2)
2 sources and how they were checked
Where sources disagree:Date the proposal was submitted: the cover says August 31, 1955 (proposal p. 1)/ “sent on September 2” (Grace Solomonoff 2016 p. 6, who says she saw the foundation’s records)/ “submitted in August 1955” (Nilsson 2010 p. 77)
The Navy's announcement and the newspaper headline
In July 1958, the U.S. Navy gave a demonstration for reporters in Washington. The Weather Bureau's large computer, an IBM 704, became able to tell whether a mark on a card was on the right or the left after about 50 trials. The wire-service UPI's article reported that the Navy expected this “embryo” (a stage before birth) to be able, in time, to walk, talk, see, write, reproduce itself and be conscious of its existence. In the article, Frank Rosenblatt said it would be the first machine to think like the human brain, that it would be wrong at first but get wiser with experience, and that it might become an exploration craft sent to other planets. The dedicated machine (the perceptron) did not yet exist, and was planned to be built over about a year for $100,000.
The popular story:People tend to say “Rosenblatt said ‘the perceptron will walk, talk and be conscious’” The original source says:according to the article, the one that held that hope was (in the UPI wire story). In the article Rosenblatt himself also made big forecasts: that , and that . But in his 1961 report he criticized the way newspapers covered it in 1958, saying it was like , and wrote that the perceptron is above all a model of the brain. Also, the demonstration was not on a dedicated machine but a simulation on a general-purpose computer, the IBM 704 (the dedicated machine had not yet been built).
What we still don’t know:The article does not make clear whose statement within the Navy the Navy's expectations came from.
Herbert A. Simon and Allen Newell predicted that within ten years a computer would become the world chess champion (unless the rules barred it from competition).
What happened next:As of April 1967, one of the strongest chess programs (MIT's MAC HACK VI) played at the level of a mid-ranked amateur (1450 on the American rating scale). In 1968, International Master David Levy and some researchers made a bet on whether a computer could beat Levy within ten years. In 1978 Levy beat the computer and won the bet. A computer beat a reigning world champion (Kasparov) in a six-game match about 40 years after the prediction, in May 1997 (IBM's Deep Blue, 3.5 to 2.5). Note that a computer has never won the title of human world champion itself (the prediction also says ).
What the figure shows:Without knowing the words “right” and “left,” the perceptron only adjusted its weights when it was wrong, learning which side each square should vote for. Even after about 50 cards, its weight board contains only the combined effect of the cards it got wrong.
Errors per 5 cards
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u03_perceptron_cards.py
04Chapter 04 · The 1960s
Search, Reasoning and a Big Prediction
How should we search a maze to find the exit fast?
The first AI was good at solving problems with clear rules, like mazes and puzzles, by searching. A* (1968) picks the next place to check by adding the estimated distance to the goal to the distance traveled so far. In the figure on the right, compare searches with no estimate, with A*, and with the estimate tripled. With a good estimate, the shortest route is found with little searching. If the estimate is made too large, the search is fast but no longer finds the shortest route.
ELIZA (1966) only spotted keywords and rearranged sentences by rules, yet it seemed to be talking with a person. In 1968 in Japan, a machine that read postal codes was shown to the public.
Big predictions came too. In 1965, Simon wrote that a person can do.
What you think you knowThe popular story:Simon predicted that in 20 years machines would take all human jobs The original source says:The original paper went on to say this was a forecast of technical ability and said nothing about how machines would be used.
Sources & confidence (4)Search, Reasoning and a Big Prediction
July 1968Verified in the original
The A* (A-star) pathfinding method — searching by the distance so far plus an estimate to the goal
Peter Hart, Nils Nilsson and Bertram Raphael published the paper . For the problem of finding the lowest-cost route in a graph of connected points, they built a theory that brings in hints from the problem itself (a heuristic: a shortcut based on experience or estimates) and showed that one search method is optimal (from the paper's abstract). According to Nilsson's recollection, for the path search of the robot “Shakey,” they took the idea of using the to the goal as the estimate (Nilsson) and added to it the idea of (Raphael). Hart then showed that as long as the estimate never exceeds the actual remaining distance, the shortest route is always found. This search method was named A*, and today it is used in places such as car navigation route guidance and games (Nilsson 2010).
ELIZA, a program that converses in text. One aim of its author's paper was to explain away a magic that seems impressive
Joseph Weizenbaum of MIT presented in a paper ELIZA, a program that can converse with a computer in text. It finds keywords in a sentence typed by a person and rearranges them according to rules to produce a reply. The role of the conversation partner can be changed by swapping a , and as of 1966 there were scripts in Welsh and German as well as English. At the start of the paper, the author writes, in effect, that if the inside of the program is explained in plain words the magic crumbles and it is seen to be just a collection of procedures, and that this paper is meant for that purpose.
The popular story:People tend to think “ELIZA was built to be an AI that could converse like a person” The original source says:in the 1966 paper by its creator, he writes at the start that when it is , and that . Explaining away something that seems impressive was one of the aims of the paper (for the story of how, in his 1976 book, he himself warns about AI, see u05).
1 July 1968Verified in the originalSources disagreeJapan
Automatic reader-sorter for handwritten postal codes (Toshiba and the Ministry of Posts, 1968)
On July 1, 1968, the day the postal code system began, the automatic postal code reader-sorter (TR-3 and TR-4), which Toshiba had developed under the guidance of the Ministry of Posts, was shown at the Tokyo Central Post Office. It is said to be the world's first machine to recognize digits that people had written freely by hand and sort mail with them. The developers analyzed about 300,000 handwritten digits collected from across the country to find which quirks in letter shapes appear most easily, and used an optical filter to erase the red frame so that only the strokes of the digits were extracted. It read the first 3 digits at a speed of about 6 items per second, and characters it could not recognize were marked as “reject” and passed to people.
What we still don’t know:The statement that it was (translated) comes from the accounts of Japanese academic societies, museums and companies. We have not opened any source that compares it with machines from the same period in other countries.
4 sources and how they were checked
Where sources disagree:When development began: 1965 (Showa 40) (Postal Museum, Toshiba 2022)/from 1966 (Showa 41) (a 1969 paper by the developers). Processing speed: 20,000 items per hour (Information Processing Society of Japan)/22,000 (Postal Museum)/about 6 per second (the 1969 paper; about 21,600 per hour when converted).
Simon's prediction (1965 book/originally a 1960 paper)
In his 1965 book, Herbert Simon wrote that within 20 years machines would be able to do any work a human can do. In the 1960 paper it was based on, he wrote that in a period much shorter than 25 years machines would have the to replace any human function in organizations. Immediately afterward, however, he went on to say that what is technically possible is separate from how it is actually used. He then assumed that, in the long run, nearly everyone who wants to work can work (full employment), and argued that the division of labor between people and machines is decided by (each side takes on what it is relatively better at).
The popular story:People tend to say “Simon predicted that machines would take all human jobs in 20 years” The original source says:the original paper was a forecast that machines would have . Right after, he writes that even though such capability is predicted, the forecast . And he thought full employment would continue in the long run (comparative advantage). In 1966 he answered a book reviewer that what decides the level of employment is the workings of the economy, not technology.
What happened next:No source was found saying that by 1985 machines could do any human work. Nilsson (2010) says that, even as of 2010, Simon's similar statement from 1957 (that the range of problems machines can handle would become as wide as the human mind) was still far from coming true. Simon himself, on the other hand, thought of technical capability and employment separately and expected that, over the long run, unemployment would not rise (in his 1966 reply he wrote that the unemployment rate was below 4% and falling).
What the figure shows:Adding an estimate of the remaining distance to the goal finds the shortest route while checking fewer squares, but an estimate that is too large checks even fewer squares at the cost of the shortest route. Moving just 1 estimate slider lets readers feel where that gain turns into a loss.
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u04_astar_maze.py
05Chapter 05 · 1966–1980
The Winter After the First Boom
Did the come in the same year in the US, the UK and Japan?
This is the time said to have brought an , when results fell short of hopes and research funding shrank. The 1966 US report on machine translation, the 1969 book and the 1973 Lighthill report in the UK followed one another.
But line up the events of the three countries in the figure on the right, and the winter did not arrive in step. In Japan, the national project “Pattern Information Processing System” began in 1971. Neural network research that leads to today's AI was also born: the Associatron in 1972 (recalling the whole from a part), the Neocognitron in 1979 (recognizing shapes even when shifted in position), and more. Move “Current year”, and even for the same year, sources give different answers: , or “there was no winter”.
This chapter runs 19 mechanisms, including the wall a single straight line cannot cross (XOR), the combinatorial explosion, beam search for spoken language, DP matching that evens out the speed of a voice, and a way to find the parts of a face.
What you think you knowThe popular story:1974–1980 was an AI winter, and research stopped The original source says:The membership of ACM's AI special interest group nearly tripled from 1973 to 1978. Whether it was an depends on what you use as the yardstick.
Sources & confidence (4)The Winter After the First Boom
1974–1980Weakly confirmedSources disagree
From which year to which year was the ? The answer differs by source. Some historians say
Japan's white paper from the Ministry of Internal Affairs and Communications (2016) calls the 1970s “the winter years” (translated), and Wikipedia gives 1974 to 1980. On the other hand, the researcher Nilsson (2010), who wrote a history of AI, calls about 1975 to 1985 the of AI and says the came in the late 1980s. And the historian Haigh (2023) argued “There Was No ‘First AI Winter’,” pointing out among other things that the membership of SIGART, the AI special interest group of the computing society ACM, nearly tripled from 1973 to 1978. In fact, an early example of the term is its use in 1984 as a word expressing worry about a winter that might be coming.
The popular story:It is often written that “1974–1980 was an AI winter, and research stopped” The original source says:it is true that in the 1970s funding became tight at some labs in the United Kingdom and for speech and robot research in the United States. But the membership of the ACM AI special interest group (SIGART) nearly tripled from 1973 to 1978 (Haigh 2023), and Nilsson calls 1975 to 1985 the . The term itself first appeared, as an early example, in 1984 as a word expressing worry about a winter that might be coming (at a panel discussion at AAAI-84), and calling the 1970s the is a name given afterward.
What we still don’t know:We have not found figures that line up total AI research funding in the 1970s by country and by year. Whether it was an changes with what you use as the yardstick (the budgets of large labs/the membership of the society/how the words were used)
7 sources and how they were checked
Where sources disagree:The period of the winter: the Ministry of Internal Affairs and Communications FY2016 white paper says the 1970s/Wikipedia says 1974 to 1980 (cited in note b of Haigh 2023)/Chilton (UK) says nearly 10 years from 1973/Nilsson 2010 says about 1975 to 1985 was boomtimes and the winter was the mid to late 1980s/Haigh 2023 says there was no winter in the broad sense in the 1970s/NRC 1999 says DARPA's AI research funding to major universities did not fall much and changed direction. It also differs by country and field: Edinburgh in the UK, and speech in the US (voices at the 1984 venue said it shrank in the late 1970s) and robotics (SRI) had a hard time, but the membership of the ACM AI group (SIGART) was growing.
The book by Minsky and Papert shows mathematically the limits of simple neural networks
A book by Marvin Minsky and Seymour Papert of MIT that examined, with mathematics, the power of the “perceptron,” the learning machine Rosenblatt built in the 1950s (a way of doing pattern recognition with a neural network). They proved that if the number of points each part can see is limited, the machine cannot recognize things more complicated than (XOR), such as (whether the number of points is even or odd) and (whether a figure is a single connected piece). About multilayer networks, they wrote their “intuitive judgement that the extension is sterile,” while also saying that confirming (or dismissing) this is an important research problem (p.231, as cited by Pollack).
The popular story:People often say “Perceptrons proved that brain-inspired machines cannot solve XOR (so they are useless altogether)” The original source says:what the book proved are the limits of a one-stage machine in which the range each part sees (the order) is limited (parity, judging whether a figure is connected, and so on). That machines with stacked layers are useless was, even in the book, only an “intuitive judgement,” and it was written as a research problem to be checked (p.231, as cited by Pollack). The book called it .
5 sources and how they were checked
Where sources disagree:Accounts differ on what the book said about multilayer networks (networks with stacked layers). It is often said that “it proved that even multiple layers are no good,” but on p.231 of the book as cited by Pollack, it is written as an “intuitive judgement” (), and confirming (or dismissing) it is called an important research problem. The cited page, p.231, follows Pollack's wording (the book itself has not been checked).
A report by James Lighthill, a leading figure in fluid dynamics, who surveyed AI research alone at the request of a British research funding body (the Science Research Council, SRC). He sorted AI into A (automation), B (the “bridge” work such as building robots) and C (studies of the brain and nerves using computers), and while he rated A and C, he was harsh on B. As a major reason for the lack of progress, he pointed to the failure to notice the phenomenon in which the number of combinations to be searched grows explosively (the combinatorial explosion). After this report, trust in AI research in Britain and its funding fell sharply.
The popular story:People tend to say “the Lighthill Report said AI is no good at all” The original source says:the report acknowledged some results in A (such as factory automation) and C (studies of the brain and nerves using computers); what it was harsh on was B (the , centered on building robots) and the goal of general-purpose AI. It cited a research plan for automating factory assembly announced by the Japanese government as an example along the lines of A, and also wrote that automating factory assembly within A. Also, the report was commissioned not from a committee but as the “personal view” of Lighthill alone, , and the SRC published it together with four other texts with different views (by Sutherland, Needham, Longuet-Higgins and Michie).
5 sources and how they were checked
Where sources disagree:The date of the report: the main text says July 1972, IEEE Spectrum (2025) says it was completed in March 1972, Nilsson's note says it was published in 1972, and Chilton says it was published in early 1973. Effect on the United States: the NRC (1999) cites Fleck (1982) and writes that it changed the direction of DARPA's research funding. But in the same note it also writes that Amarel (1988) said it had no effect.
Kaoru Nakano (University of Tokyo)'s : a brain-inspired memory that recalls the whole when shown a part
Kaoru Nakano of the University of Tokyo presented the “Associatron,” a mechanism that stores information as patterns of 0s and 1s spread across a whole network and recalls the whole from a part of it. The larger the clue, the more accurately it recalls, and the smaller the clue, the more vaguely. It is a simplified model of the network of nerves in the brain, and he showed it could be built with elements connected only to their neighbors working at the same time. He ran experiments on a computer and also showed examples of applying it to concept formation and to games.
The popular story:People tend to say “neural networks for ‘remembering’ memories began with Hopfield in 1982” The original source says:ten years earlier, in 1972, Kaoru Nakano of the University of Tokyo had published the Associatron in an IEEE journal. The explanation of the 2024 Nobel Prize in Physics also lists it among its references (but it does not name him in the main text and only touches on it within a range of reference numbers).
What the figure shows:The dates of an AI winter vary greatly depending on which source is used as a guide. In Japan, major projects and neural network research were starting around the same time.
06Chapter 06 · 1975–1990
Writing In the Knowledge of Experts
Line up rules: what can they do, and what can't they?
The second boom began with AI that writes experts' knowledge in as rules (expert systems). MYCIN, from 1972, was research on advising which drug to choose for an infection. It combined rules with certainty factors (how likely something is), and when asked “Why?”, it answered by showing the rules it had used.
The figure on the right runs the same mechanism on a bicycle's condition (it gives no medical advice). Press the known facts to switch them, and usable rules fire one after another, changing the conclusion and its certainty. For a symptom with no rule, it can answer nothing. The effort of writing in more knowledge became the limit of this method.
In 1987 in Japan, the Sendai subway began running with fuzzy control, which mixes in vague rules.
What you think you knowThe popular story:The second boom went too far because of researchers' big promises The original source says:A 1984 article said most researchers came to talk about small steps of progress, and it was some of the companies with exhibits that acted as if the dream had already come true.
Sources & confidence (3)Writing In the Knowledge of Experts
1972–1984Verified in the originalSources disagree
MYCIN: an AI of rules that advises doctors on choosing drugs for infections. Its evaluation matched specialists, yet it was not used routinely in hospitals
At Stanford University, Edward Shortliffe, then a medical student, and his colleagues developed MYCIN, a program that advises doctors on choosing drugs for bacterial infections (blood infections, and later meningitis). They built doctors' knowledge into it as rules of the form “if (a test result is ...) then (the germ is probably ...)” (about 200 at first, about 500 by 1978), and made it able to explain the reasons for its judgments. In a 1979 evaluation, for 10 meningitis patients, 8 infectious disease specialists from outside Stanford scored the prescriptions of MYCIN and of doctors without knowing whose they were. 65% of MYCIN's prescriptions were , while five Stanford specialists scored 42.5 to 62.5% (average 55.5%). Even so, the developers' book records that .
The popular story:People often say “MYCIN was more accurate than specialists but was not used in hospitals because of legal and liability problems” (Wikipedia also writes that ) The original source says:the reasons given in the developers' book (1984) are different. The program needed more knowledge about other infections, the experts left the university, funding to add knowledge was hard to get, the developers noticed weaknesses in the system and wanted to move on to the next research, and above all they knew that it would probably not be accepted, for ordinary reasons: decision-making performance (the book goes on to say that many of these were problems of ease of use and effort).
What we still don’t know:We have not checked who first brought up the matter of law and liability, or when.
4 sources and how they were checked
Where sources disagree:Differences in the evaluation figures: Nilsson cites 70% and 75% (better than the level of agreement among the Stanford faculty). The 1979 paper itself gives 65% for the share accepted (the 5 faculty: 42.5–62.5%) and 70% for the share approved by a majority of experts (the 5 faculty: 30–50%). Chapter 30 of the same book writes that in the earlier evaluations (studies 1 and 2) about 75% were approved by a majority. The numbers change depending on which evaluation and which way of counting.
1984: at an AI conference exhibit hall, an ad says — a record of the mood that this time it was the real thing
Science writer George Johnson described the exhibit hall at the August 1984 conference of the American Association for Artificial Intelligence (AAAI). Most researchers had come to discuss small steps forward, but some exhibiting companies acted as if the age-old dream of making intelligent companions had already come true. The brochure for TIMM, an AI tool for entering experts' knowledge, boasted and said that expert systems never get sick and never resign or retire early. The reporter wrote that the sellers' words sometimes sounded like .
The popular story:The excesses of the second boom are often blamed on researchers' big promises The original source says:According to this article, most researchers had come to talk about small steps forward. It was only some of the exhibiting companies that acted as if (the article also says that IBM, Xerox, TI, DEC and others were modest).
What we still don’t know:The article does not name the company that sold TIMM.
Sendai's subway opens, using (translated) (AI with rules that handle vagueness) for automatic train operation
The Sendai city subway (the ninth city subway in Japan) opened on July 15, 1987. The automatic train operation system developed by Hitachi adopted (translated). It used AI (knowledge engineering) rules written in (translated) (the form 'if so-and-so, then do so-and-so') to replace the skills of expert drivers. The article says that better ride comfort, better stopping accuracy and energy saving were achieved, and introduces this predictive fuzzy control as (translated) (the words of the article by the company that made it).
The popular story:Fuzzy is often thought to be a buzzword of home appliances The original source says:Before home appliances, it was used in the automatic operation of the Sendai city subway that opened in 1987. The company that developed it explains it as AI (knowledge engineering) rules in “IF-THEN form” (translated) (written as one of the second-boom AIs that build in knowledge).
What we still don’t know: (translated) is the words of an article by the company that made it, and has not been confirmed in other sources.
What the figure shows:Rules work one after another from known facts to reach a conclusion and can explain their reasons. But they cannot answer anything their rules do not cover.
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u06_expert_rules.py
07Chapter 07 · 1979–1995
Japan's Fifth Generation Computer
What did the national project aim at, and what did it leave behind?
In 1982, Japan began a plan for a new kind of computer centered on reasoning and knowledge processing. It was named , coming after the generations of parts (vacuum tubes, transistors, ICs and LSIs). The world reacted, and the UK and the US also began big projects.
The central tool was Prolog, a logic programming language. You line up facts and rules, and it answers questions by reasoning. In the figure on the right, find “grandparent” and “cousin” from family facts. The number of fact lookups is the effort of reasoning. In 1992, the parallel inference machine PIM/p could make 156 million inferences per second.
In the final evaluation, the target for reasoning speed was beaten, but a mechanism for conversing with people was never built. Whether it was a depends on what you take as the goal.
What you think you knowThe popular story:The Fifth Generation failed The original source says:The final evaluation wrote that it (translated). Judgments differ depending on what you take as the goal.
The 1981 forecast: it is said that in the early 1990s computers with eyes, ears, and a mouth, that understand speech and can do automatic translation and interpreting, will appear
The report of the survey before the plan (1979–1981; chaired by Tohru Moto-oka of the University of Tokyo) stated that the goal was to complete a prototype in the year 1990. A booklet explaining it for the general public wrote that fifth-generation computers are (translated) and that research must start early to (translated) (to build a trial machine). As the pictures of what they aimed for, it listed eight functions, including (translated) that can handle sound, figures, images, and characters as they are; (translated) that can be spoken to in everyday language (and so can also do automatic translation and interpreting); computers that have common sense and solve unfamiliar problems by reasoning; and computers that can be used without writing programs.
The popular story:It is said that the Fifth Generation promised to build, in 10 years, a computer that can talk like a human The original source says:The 1981 survey documents do say “computers that understand speech” (translated), (translated), and (translated) (a trial machine). However, in 1992 the director, Kazuhiro Fuchi, said that in the project that actually began in 1982, building applications such as machine translation had been dropped from the goals and the project was narrowed to machines for reasoning. The story changes depending on which year's, and which document's, goals you mean.
What happened next:The project ran in fiscal years 1982–1992. According to the 1993 final evaluation report, the goal for inference speed (100 million per second) was met and exceeded, at over 150 million per second. On the other hand, the report says that systems that interact with people by voice or images turned out to need a huge amount of background knowledge, so partway through the project narrowed its focus to a base for language research and did not get as far as building concrete systems. In 1992 the director, Kazuhiro Fuchi, said that building application systems such as machine translation had been dropped from the goals when the project began in 1982.
What we still don’t know:The (translated) (1981; 7 groups, 26 tasks), which are said to set numerical goals such as the number of words translated and accuracy, could not be found and have not been checked.
Computers of the Fifth Generation (booklet) (Japan Information Processing Development Center (JIPDEC) (incorporated foundation) · 1981 · p.参1 Reference: Functions of fifth generation computers · Original source)
1 June 1992Verified in the originalSources disagreeJapan
Fifth Generation results: the Parallel Inference Machine PIM and the language KL1 (the largest machine had 512 computers; the five models together exceeded 1,000)
The Fifth Generation project developed the “Parallel Inference Machine PIM”, which links many computers to carry out inference (drawing conclusions from rules) at the same time, and its dedicated language , and presented them at the international conference FGCS'92 in June 1992. KL1 was designed by Takashi Chikayama, based on the mechanism of the language GHC devised by researcher Kazunori Ueda (from a talk by director Kazuhiro Fuchi). Five models of PIM with different specifications were built; the largest, PIM/p, used 512 computers and could perform 156 million inferences per second. Counting all five models together, there were more than 1,000 computers. The final evaluation states that the target of 100 million inferences per second was exceeded.
The popular story:“The Fifth Generation built an inference machine linking 1,000 computers,” people tend to say The original source says:The largest single machine was the 512-computer PIM/p. Counting all five models together, there were more than 1,000 computers, which is how the final evaluation words it
What we still don’t know:We have not confirmed how PIM was used after the project (how many machines ran where, and for how many years)
4 sources and how they were checked
Where sources disagree:Differences in how the scale is described: the conference page of the ICOT Archive says “a prototype of a parallel inference machine on the scale of 1,000 computers”; the final evaluation says “five models totaling more than 1,000, starting with the 512-computer model p”; Nilsson says “the largest, PIM/p, has 512”
Fifth Generation Computer Project: Final Evaluation Report (Academic and Technical Evaluation Working Group, Committee for the Promotion of Basic Computer Technology Development · 1993 · p.8 Parallel symbolic processing technology (and PDF pages 5, 1… · Original source)
June 1992–1995Verified in the originalSources disagreeJapan
The story that “the Fifth Generation Computer failed”: what the people involved, the evaluation committee and outside researchers each wrote
In June 1992, right after the international conference that wrapped up the project (FGCS'92), an editorial in the newspaper The Baltimore Sun (written for American companies) wrote of the project's . But in the keynote speech at that conference, the director, Kazuhiro Fuchi, introduced the situation by saying (translated). He then explained that big images such as (translated) and (translated) had spread from the 1981 conference before the project. He said that the project begun in 1982 had a more modest content (parallel inference), and that he believed it was a success. The promotion committee's final evaluation (1993) also said it had “fully met the initial expectations” (translated). A report of the Ministry of International Trade and Industry's research institute (1995) wrote that calling it a failure because it did not become a product is an opinion that does not fully understand the project's aims (basic research and international contribution). At the same time, the same report also writes that the structure of the computers made is not expected to be used in future technology, because of the progress of small computers. A history book by an outside researcher (Nilsson 2010) writes that many people think most of the results now have only historical significance.
The popular story:It is said that “the Fifth Generation Computer failed (and Japan admitted it)” The original source says:At the 1992 conference, the director did not admit failure. He said the source of the (translated) was the big dream image of 1981, and that the project goals from 1982 (parallel inference) were achieved. The promotion committee's final evaluation too said it had “fully met the initial expectations” (translated). However, the fact that the hardware and software developed did not spread is written in both the report of the Ministry of International Trade and Industry's research institute and the book by an outside researcher. The answer changes depending on what you take as the goal.
What we still don’t know:Where the reputation of first spread from in the United States (for example the June 1992 New York Times article ) has not been confirmed, because we could not open that article.
5 sources and how they were checked
Where sources disagree:About the same June 1992 conference, the newspaper editorial wrote that the failure was acknowledged. The director's keynote introduced that there are commentaries saying it is a failure, and then said he believes it was a success. What statement (whose words) the editorial based its “acknowledged” on is not written in the editorial.
What the figure shows:With facts and rules in place, reasoning can answer questions. But the more distant the relatives, the more work it takes to check the facts.
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u07_mini_prolog.py
08Chapter 08 · 1987–2005
Winter, and Sprouts Growing Quietly
How does a network with stacked layers learn?
The expert-system business slowed, and the second AI winter came. Meanwhile, technology that learns from data was quietly growing. In 1986, Nature published a paper on training multilayer neural networks with backpropagation.
The figure on the right shows a network with a hidden layer learning XOR. The error at the output is passed from the back layers to the front ones, and the weights are corrected little by little. XOR, which one layer could not learn, can be solved by stacking layers. In the graph below, the error goes down.
Around the same time came the network that can remember a long context (LSTM, 1997), the support vector machine that draws the widest road between groups of data (1995), and backgammon that learns by playing itself (1992).
What you think you knowThe popular story:Hinton invented backpropagation The original source says:Other researchers had independently discovered it before the 1986 paper. In Japan, Shun'ichi Amari also published a theory in 1967 of learning by correcting errors little by little.
Sources & confidence (4)Winter, and Sprouts Growing Quietly
9 October 1986Verified in the originalSources disagree
A paper on training multilayer neural networks with backpropagation appears in Nature
Rumelhart, Hinton and Williams announced a way of training neural networks that have between input and output. The difference between the output and the correct answer (the error) is passed back from the output side to the input side step by step, and the strengths of the connections are updated bit by bit (passing the errors backward, as in the paper's title , is backpropagation). They showed by experiments that the hidden layers come to represent features that nobody taught them.
The popular story:It is often said that backpropagation was invented by Hinton The original source says:The 1986 paper itself writes that (by Parker and by Le Cun). The Nobel committee's explanation also says that , and names, as the more important point, that the three showed that . Even earlier, the names of Linnainmaa of Finland (1970), Werbos of the United States (1974, 1982) and Shun'ichi Amari of Japan (1967) come up.
What we still don’t know:People could read what is represented inside the hidden layers in this paper's small example (a family tree). But in large networks, only parts of it are understood even now (this connects to the unit on the fourth boom).
6 sources and how they were checked
Where sources disagree:Who “first thought of” this learning method differs depending on the writer (we do not decide which is right). (1) The 1986 paper itself: it says Parker and Le Cun discovered variants separately. (2) Nilsson (2010): the earliest is probably Bryson and Ho (in the field of control), and he also lists Werbos's doctoral thesis (1974). (3) The Nobel committee (2024): the three reinvented the method that Werbos (1982) and Linnainmaa (1970/1976) had already used. (4) Schmidhuber (2014, 2022): Linnainmaa in 1970 was first, the first application to neural networks was by Werbos (1981/1982), and in 1967 Shun'ichi Amari trained a multilayer network by gradient descent, and he sees a forerunner in Kelley in 1960. Schmidhuber is himself a researcher close to being a party to the matter, and takes a strong position in this story.
The worst-case scenario of “The AI Winter” drawn in a 1984 discussion ── checking the answers afterward
At the conference of the American Association for Artificial Intelligence (AAAI), a panel discussion was held titled The moderator, Drew McDermott, said that behind the bustle in industry, there was deep unease among people who had researched for many years, from a worry that . As the worst-case scenario he drew this picture: in five years America's fails, Japan's Fifth Generation also hits a dead end, start-up companies go under, funding for AI stops, and everybody changes the names of their research to something else. He introduced the fact that some people call this state “The AI Winter.” But he also said he thought it unlikely. In the discussion, another researcher (Roger Schank), when asked whether he thought a catastrophe would come, said that he told them it would. On the other hand, the view was also put forward (the same person went on to say that the bubble might not burst but shrink a little).
The popular story:It is often said that the 1984 discussion predicted the AI winter exactly (a warning that came true) The original source says:The moderator drew it as a , and said himself, . Even within the discussion, views ranged from a catastrophe coming to its being not a winter but a dusk. Over the next few years, many parts of the scenario (the shrinking of the strategic computing initiative, the decline in companies, the decline in society membership, the end of the Fifth Generation's main stage) did happen, but not all at once five years later
What happened next:Afterward, development of the autonomous land vehicle (ALV), one of the plan's showpieces, was cut off in April 1988. The head of the responsible division, who took up the post in 1987, also cut off parts of the AI program. The plan disappeared from DARPA's budget in 1993. Membership in the American Association for Artificial Intelligence peaked at 16,421 in 1987 and settled at 4,000–5,000 by 1996. Many of the AI companies developing expert systems disappeared, were acquired, or changed their business. Japan's Fifth Generation Computer Project ended its main stage in fiscal 1992. Nilsson writes that these events piled up in the mid-to-late 1980s and came to be called “The AI Winter.”
What we still don’t know:Whether one of the scenarios, , really happened in the 1990s has not been confirmed in original sources (a candidate dealt with in u08)
3 sources and how they were checked
The Dark Ages of AI: A Panel Discussion at AAAI-84 (Drew McDermott, M. Mitchell Waldrop, B. Chandrasekaran, John McDermott, Roger Schank · 1985 · p.122 Drew McDermott's opening talk · Original source)
LSTM: a neural network that can remember the earlier parts of a long sentence or sound is announced
Hochreiter and Schmidhuber announced LSTM, a neural network for time-series data (sequences of sounds or letters) with a built-in (a box that remembers) and that open and close what goes into and out of the box. With earlier methods, the signal used for correction in backpropagation either faded away (approached zero) or blew up as it went back in time, so they could not remember things from long ago. LSTM could hold on to and use clues from the past more than 1000 steps away.
2 sources and how they were checked
Long Short-Term Memory (Sepp Hochreiter, Jürgen Schmidhuber · 1997 · p.1735 Abstract / 1 Introduction · Original source)
Vapnik and colleagues create the support vector machine, which separates data by drawing the widest road between them
When drawing a line to separate two kinds of points, you draw the line down the middle of the widest road, as far as possible from both kinds of points. Then even points seen for the first time are separated well. Vapnik and colleagues made it so that this idea can be computed from only the few points at the edges of the road (the support vectors: the points that hold up the road). On the handwritten digits of MNIST it reached an error rate of 1.1% (Cortes and Vapnik), close to the neural network LeNet. By around 2000, this kind of method had become the mainstream in practical use.
The popular story:It is often thought that neural networks were number one all the way after the 1980s The original source says:In the ten years around 2000, methods other than neural networks (such as support vector machines) held much of practical use (Schmidhuber 2014). The 1998 LeNet paper itself also admits that this method performs well without building in knowledge about images
What the figure shows:A boundary for XOR that 1 layer could not draw gradually becomes possible by adding layers and passing errors backward to adjust the network.
Size of the error
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u08_backprop_xor.py
09Chapter 09 · 2006–2012
Learning From Data By Itself
Can new data be sorted just by memorizing lots of examples?
Thanks to huge amounts of data and GPUs, AI built from many stacked layers of neural networks (deep learning) suddenly became strong. It won by a wide margin at the 2012 image contest. Many of its tools had been growing for a long time. This chapter runs machine learning methods one by one: least squares (1805), Bayes, principal component analysis, k-nearest neighbors, k-means, decision trees, SVM, random forests, singular value decomposition, reinforcement learning, and more. It also takes up Chikio Hayashi's quantification methods, Hirotugu Akaike's AIC and Nobuyuki Otsu's binarization from Japan.
The figure on the right shows one of them, k-nearest neighbors. It remembers points with known answers, and decides the class of a new point by majority vote among its k nearest points. With k set to 1, every training point is classified correctly, but it memorizes even the noise and tends to miss on new points (overfitting). Checking by splitting the data into training and test sets is the heart of thinking in this era.
What you think you knowThe popular story:Hinton invented a new idea in 2006 The original source says:The paper from that year itself wrote that it had been clear since the 1980s that deep networks should be useful.
Sources & confidence (4)Learning From Data By Itself
2009Verified in the original
Fei-Fei Li and colleagues at Princeton University present ImageNet, millions of named photos; the people who checked them were workers hired over the internet
Li and colleagues presented ImageNet, built on WordNet, a dictionary that organizes concepts in a hierarchy, and collecting an average of 500–1,000 photos for each of about 80,000 groups of nouns (the paper's example is ). At the time of publication it had reached 12 areas, 5,247 categories and 3.2 million images. The images were collected with search engines, and workers around the world, paid through Amazon Mechanical Turk, checked one by one whether the target object was really in each picture, deciding by the votes of several people.
The popular story:People tend to say “AI learned by looking at photos on its own” The original source says:The correct labels used for training were checked and attached one image at a time by large numbers of people paid for their work over the internet (paper, page 4). A person inside the machine is not only a story about the chess automaton of 1770.
What we still don’t know:The paper does not state the number of workers, the countries they lived in, or the amount they were paid (unconfirmed).
13 October 2012Verified in the originalSources disagree
In the image-recognition competition ILSVRC 2012, the University of Toronto's deep convolutional neural network (SuperVision) wins by a wide margin. The runner-up is a University of Tokyo team
In a competition to identify 1,000 kinds of objects from photos, the team “SuperVision” of Krizhevsky, Sutskever and Hinton held its error rate, under a rule allowing 5 guesses, to 15.3% (16.4% if only the data supplied by the competition is used). The runner-up, a University of Tokyo team (ISI), scored 26.2%, a gap of about 11 points. They trained an 8-layer neural network with 60 million parameters on 2 gaming GPUs (graphics chips, made by NVIDIA). In a later paper, the competition's organizers wrote that for research on recognizing a wide variety of objects.
The popular story:People tend to say “deep learning was suddenly born in 2012” The original source says:The winning system was a large-scale version of the of LeCun and colleagues in 1989 (whose origin is Fukushima's Neocognitron of 1979), trained on GPUs. The paper itself writes that (prefaced by saying that every experiment points that way). People also tend to think “2012 was a Western story”, but the runner-up was a University of Tokyo team
4 sources and how they were checked
Where sources disagree:Training time: the team introduction on the competition page says “about 1 week”, while the paper says “5 to 6 days”. The first-place figure: there are two, 15.3% (with extra data) and 16.4% (supplied data only), and the table in the organizers' paper uses 16.4
Hinton and colleagues present a way to train a deep neural network “one layer at a time”. It is seen as an important step toward
Neural networks with many stacked layers could not be trained well by backpropagation alone. Hinton and colleagues showed a method in which, first, one layer at a time and without being given correct answers, the network learns the of the data (pre-training), and then the whole network is adjusted by backpropagation. It reached an error rate of 1.25% on the handwritten digits of MNIST (the Neural Computation paper), and it was also better than earlier methods at representing images and documents with a small number of values (the Science paper).
The popular story:“In 2006 Hinton invented the new idea of deep learning,” people tend to say The original source says:The paper itself (Science) writes that it has been for the job of representing data with a small number of values. This needs computers that are fast enough, data that is large enough, and initial weights close enough to a good solution, and it says What was new was mainly what the paper calls . In the same year, 2006, Bengio and colleagues also published a similar method (reference 34 in the Nobel committee's explanation).
The $1 million contest to predict movie tastes, the “Netflix Prize” (2006–2009): the winner was decided by a 20-minute margin
In October 2006, Netflix, which then rented out movies on DVD, opened a contest. It offered a $1 million prize to anyone who could predict movie ratings 10% more accurately than its own recommendation system (Cinematch). It distributed more than 100 million ratings (1 to 5 stars) of about 18,000 movies by about 480,000 people, with names replaced by numbers. About three years later, on September 21, 2009, the team BellKor's Pragmatic Chaos won. The second-place team had the same score (error 0.8567, a 10.06% improvement), but the side that submitted about 20 minutes earlier became the winner (under the rule that a tie goes to whoever submitted first).
The popular story:“Netflix improved its recommendations with the system found in the $1 million contest,” people tend to think The original source says:According to Netflix's own blog (2012), it put two methods from the first year's progress prize into use, but the combination of hundreds of models that won the $1 million was not adopted, because the extra accuracy was not worth the effort. Meanwhile the company had moved from DVDs to streaming, and had itself become only one part of a recommendation system. Another point: people thought “Data with the names removed cannot be traced to anyone”, but researchers showed that individuals could be identified by matching against public movie ratings, and the second contest was cancelled (an FTC letter).
What the figure shows:With k set to 1, every memorized point is classified correctly, but noise is memorized too, making errors on new points more likely. That is why data is split into training and test sets.
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u09_knn.py
10Chapter 10 · 2012–2019
Go, Shogi and Predictions About Jobs
Why does playing out randomly to the end show which moves are good?
AI beat top professionals at Go and shogi, and predictions that “jobs will disappear” were talked about around the world. An AI boom also arose in Japan, and the name “third” (boom) spread. This chapter also runs deep-learning tools one by one: autoencoders, GANs, word2vec, object detection, transfer learning, ResNet and more.
One key to strong Go play was Monte Carlo tree search (2006). After trying a move, play randomly to the very end many times, and compare moves by the share of wins. The figure on the right is tic-tac-toe. As you raise the number of trial plays, the winning chances of the good moves become clear. AlphaGo (2016) combined this with neural networks trained on human games and with self-play.
In Japan, in 2015 the Information Processing Society of Japan declared that computer shogi was (translated) with top professional players.
What you think you knowThe popular story:AlphaGo became strong by learning on its own The original source says:Even the version that beat Lee Sedol in 2016 first learned from human games as models, and then grew stronger through self-play.
Sources & confidence (4)Go, Shogi and Predictions About Jobs
9 March 2016Verified in the original
AlphaGo beats Lee Sedol, one of the world's top players, 4 games to 1 (Seoul)
In March 2016 in Seoul, South Korea, AlphaGo played a five-game match with no handicap against Lee Sedol, a 9-dan player who had won 18 world titles. AlphaGo won 4 games to 1. In Game 4, Lee Sedol won with a surprising move at move 78. DeepMind announced that it would donate the 1 million dollar prize to education and Go organizations and to UNICEF.
The popular story:People tend to say “AlphaGo got strong by itself without being taught by humans” The original source says:the version that played Lee Sedol (AlphaGo Lee) worked in almost the same way as the 2015 version, and also began by learning to imitate human games (page 21 of the 2017 paper, and DeepMind's October 18, 2017 article: ). Not using human game records began with AlphaGo Zero in 2017 (→ Is it true that AlphaGo learned and got…).
What we learned in Seoul with AlphaGo (Demis Hassabis (Google official blog) · 2016 · Main text (The final score was 4-1, move 78 of Game 4) · Original source)
The two papers behind , which made Go programs strong
In Go, there are many possible moves in a single position, and evaluating a position is hard. So search methods like those used for chess did not make programs strong. In 2006, a paper by Coulom of France presented a new search method (Monte-Carlo Tree Search, MCTS). It plays out a game at random many times from a position to the end (Monte Carlo), compares moves by their win rates, and examines the more promising branches more deeply. With his 9×9 Go program Crazy Stone, Coulom won a computer Go tournament (KGS). In the same year, Kocsis and Szepesvári of Hungary proposed UCT, a method for deciding which branch to try and how much. Ten years later, the AlphaGo paper (2016) cited these two as the MCTS literature, and combined MCTS with two neural networks (one predicting the next move and one evaluating positions).
3 sources and how they were checked
Where sources disagree:Which edition of the conference the Kocsis and Szepesvári paper was at: the AlphaGo reference list says “15th European Conference on Machine Learning”, while Springer's bibliographic record says ECML 2006 was the 17th (we only confirmed this in search results and did not open the original). We have not settled which is right.
The Information Processing Society of Japan declares an end to its project, saying computer shogi has
From 2010 the Information Processing Society of Japan (IPSJ) had been running a project aiming to achieve (note 1). In October 2015 it declared the project finished, saying . “Caught up” did not mean winning every time; it was explained to mean that, over many games, the computer is likely to come out ahead. At that point, however, a direct match against a top professional had not yet taken place.
What happened next:About a year and a half later, on April 1 and May 20, 2017, the shogi software PONANZA beat Amahiko Sato, the Meijin (the top title holder; he played as Eiō), in both games. The organizers ended the Denōsen matches with this contest.
Oxford University study: (risk of being replaced by computers; 2013)
In September 2013, Carl Benedikt Frey and Osborne of the University of Oxford published a paper estimating the probability that computers would replace workers in 702 occupations in the United States. It says that 47% of U.S. employment falls . The figure was later taken as “a prediction that jobs will disappear” and became a target of checking (for example, the title of a 2022 ITIF article, , from a separate record this site keeps, checking predictions about work against what happened). The details and the later checking are recorded in a separate study, apart from this site, on checking predictions about work in the age of AI.
The popular story:People tend to say “47% of American jobs will disappear in 10 to 20 years” The original source says:What the paper says is that 47% of employment is in the high-risk category and that such occupations could be automated within an unspecified number of years (perhaps a decade or two). It is not a forecast of how many jobs will actually disappear (the later checking is covered in the separate study, apart from this site, on checking predictions about work in the age of AI)
What the figure shows:Even random play, repeated many times, clearly reveals which good moves are more likely to win.
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u10_mcts_connect4.py
11Chapter 11 · 2017–2022
AI That Makes Text and Images
Which words does a text-writing AI “pay attention” to?
From the mechanism shown in a 2017 paper (the transformer), AI that makes text and images developed, and in 2022 it arrived in a form anyone could use.
One core part of the mechanism is . It decides with numbers how much one word in a sentence looks at each of the other words. In the figure on the right, switch the word you ask about. “Ate” looks hard at who ate (the cat) and at what was eaten (the fish). The numbers are a small example made by this site, not values from a real AI.
An AI that writes text uses this mechanism to work out the probability of the next word and pick words one at a time.
What you think you knowThe popular story:ChatGPT reached 100 million people in 2 months The original source says:That was not the company's announcement but an estimate by a bank's analysts, worked out from web visits.
Sources & confidence (3)AI That Makes Text and Images
12 June 2017Verified in the original
The Paper on , the Basis of Today's Text AI, Is Published
Eight people, researchers at Google and a University of Toronto student, presented a new AI architecture (the Transformer) built only from “attention mechanisms,” which pay attention to which words in a sentence relate to which other words. The paper tested it on tasks such as translating English into German and French, and it achieved better results than before with shorter training time. The later GPT and BERT are built on this architecture (confirmed in their respective papers).
The popular story:People tend to think of it as “a paper for building conversational AI (chat AI)” (the popular story is this site's own inference) The original source says:What the paper tested was translation and English syntactic parsing. The next goals it named in its conclusion were applications to images, audio and video, and conversation does not appear in the main text
OpenAI released the conversational AI . The announcement says it can answer follow-up questions, admit its mistakes, challenge incorrect premises, and reject inappropriate requests. Inside, it is a sibling of GPT-3.5 whose training finished in early 2022, tuned by having humans score its answers. It was free during the “research preview,” and the stated purpose was to collect users' feedback.
The popular story:People tend to think “ChatGPT was launched with great fanfare as a new, perfect AI” (the popular story is this site's own inference) The original source says:The announcement called it a . Inside was a model whose training had finished earlier the same year, and from the day of the announcement its weakness was stated: it
What we still don’t know:As one reason it is hard to fix mistakes, the announcement gives that (RL means reinforcement learning). Why and when plausible-sounding mistakes (later called ) happen was something the developers, even at this point, still wrote .
1 February 2023Verified in the originalSources disagree
“ChatGPT Reached 100 Million Users in 2 Months” Is Not a Company Announcement but an Estimate by a Bank's Analysts from Web Visit Counts
In February 2023, news spread around the world that “ChatGPT was used by 100 million people two months after release and became the fastest-spreading app in history.” Traced back, the source was a memo by analysts at the investment bank UBS. Using figures from the web analytics company Similarweb, it concluded that ChatGPT (translated) (the quoted words are the wording of the Reuters article that reported the memo). Reuters wrote “estimate,” and Similarweb had not answered requests to confirm the figures at that time. In the body of The Guardian's article, it is presented as Similarweb's figure of (translated).
The popular story:The story spread that “ChatGPT was used by 100 million people in 2 months (the company's record)” The original source says:The source was a memo by UBS analysts, (translated) based on Similarweb's visit counts. Neither of the two articles presents it as an announcement by OpenAI. “Unique visitors” (translated) can count the same person separately when they come from different devices, so it is not necessarily the number of people (this point is this site's own note).
2 sources and how they were checked
Where sources disagree:Reuters writes the same number as “monthly users (estimate),” while the body of The Guardian writes “unique visitors (Similarweb).” The words used for the counting do not match.
What the figure shows:Numbers determine which other words in a sentence a word pays attention to, and how much. The word “ate” pays attention to who did it (the cat) and what was eaten (the fish).
This is the same mechanism as "Try it", written as Python code. Press ▶ Run and the result appears below. Change the numbers and run it again.
u11_attention.py
12Chapter 12 · 2023 and After
Predictions Waiting to Be Checked
If you extend a straight line, do you know the future?
Many of today's predictions rest on the assumption that the link between bigger AI and better performance will keep going. The figure on the right lines up the amount of computation used to train AI (data from Epoch AI) on a scale that grows by 10 times at each step. Draw a line through the points up to some year and extend it, and you have a prediction of the future. Move the year where the line is drawn, and the pace of the prediction changes.
Predictions do not only miss. In 2022, two researchers forecast whether by 2025 an AI would score at gold-medal level in the International Mathematical Olympiad, and in July 2025 it happened. On the other hand, an international report writes that even the people who built today's big AI can barely read what goes on inside it.
Whether a winter will follow the fourth boom is still unknown. This chapter lays out the material without giving an answer.
Sources & confidence (3)Predictions Waiting to Be Checked
23 January 2020Verified in the original
A Paper on a Law Where Performance Rises at a Fixed Rate as Models Grow — but the Authors Themselves Note
Researchers at OpenAI and Johns Hopkins University showed that a language model's results (measured by how hard it is to guess the next word) improve in a clean, fixed form (a power law) as the number of parameters, the amount of training data and the amount of computation increase. This form held over more than seven orders of magnitude (10 million times). This idea became one of the foundations of the later race to build ever larger AI.
The popular story:People tend to take it as “a law that says the bigger you make it, the smarter it gets without limit” (the way it is taken is this site's own inference) The original source says:The original paper itself writes and .
What we still don’t know:What is known: in the range studied up to 2020, performance rose by a fixed rule as scale increased. What is not known: how far this continues and why it happens (the paper itself writes that the trends and that ).
Will AI Win Gold at the Math Olympiad by 2025? In 2022 Two Researchers Forecast Under 8% and Over 16%; the Result Came in July 2025
The AI researchers Paul Christiano and Eliezer Yudkowsky differed in their views on the progress of AI. So, as a prediction that can be settled one way or the other, they publicly gave their probabilities that, at the International Mathematical Olympiad (a high-school competition), an AI (translated) (the rules, such as time, follow the IMO Grand Challenge). Christiano said under 8%, and Yudkowsky said 16% or more. For solving the hardest problem, Christiano predicted under 4%. In July 2025, Google DeepMind announced that an enhanced version of Gemini had fully solved 5 of the 6 problems and earned 35 points out of 42 (a gold-medal score), formally graded and confirmed by the competition's graders. It wrote its answers in ordinary language within the 4.5-hour time limit.
What happened next:In July 2025, an enhanced version of Google DeepMind's Gemini earned 35 points out of 42 (a gold-medal score). The competition's graders formally graded it, and the president of the International Mathematical Olympiad confirmed it as (translated) (however, according to the blog, the confirmation was of the answers, not a check of how the AI works). It was done within the 4.5-hour time limit, and the hardest problem (Problem 6) was not solved (5 of 6 problems). Because both predictions are probabilities, neither can be called right or wrong outright, but the actual result was closer to the side that had put the probability higher (over 16%).
International report by 96 experts (including an advisory panel chosen by 30 countries and others): and
Following the Bletchley meeting (2023), 96 experts chaired by Yoshua Bengio (including an advisory panel chosen by 30 countries and the UN, EU and OECD) compiled an international report on AI safety (Hiroaki Kitano took part from Japan). The report explains that general-purpose AI models are but are built through learning, and wrote that and that . On future progress, it said the capabilities of general-purpose AI , and that experts . The second report of February 2026 also points out that and that (inputs: computation, algorithm improvements and data).
What we still don’t know:What we still don't know (points made by experts chosen by the countries): (1) The inner workings of modern large AI (the inner mechanisms are largely unreadable even to the developers, and explanation techniques are severely limited). (2) The pace of future progress (anything from slow to extremely rapid is possible; experts disagree about how far scaling will keep working). The 2026 report shows the same uncertainty continuing.
What the figure shows:The predicted future pace changes greatly with the last year of data used to draw a straight line. Extending that line into the future assumes that its conditions will continue.
13Chapter 13 · Overview
Waves, Prediction Map, and Unknowns
How many years ahead have AI predictions looked?
Finally, we study this site's own records as data. The figure on the right is a map of predictions. The horizontal axis is the year of the prediction, and the vertical axis is the year in which it said “by this year”. Nearby points are shifted slightly to make them easier to tell apart, and thin lines connect them to their original year positions. If the original year position is above the line for the current year, the prediction's year has not yet come.
A well-known study (2012) found that AI predictions are mostly 15 to 25 years ahead. But on the first page of that paper there is now a note: . The answer changes with how you count and how you collect.
Some predictions in national teaching materials also changed shape when traced to their source. (translated) was originally a figure in a 2005 book about forecasts of computing speed.
What you think you knowThe popular story:Every new technology follows “peak of hope The original source says:valley of disappointment → settling down” → When researchers checked whether things happen as in the research firm's chart, even the firm's own records did not match. The same pattern each time is a story that looks that way when you line things up, not a fixed law.
Sources & confidence (2)Waves, Prediction Map, and Unknowns
2012Verified in the original
A study finding that AI predictions mostly fall (the paper's first page now carries the note )
A paper that collected and analyzed 95 predictions of when AI would arrive. The most common prediction was , and it concluded that predictions by experts and non-experts cannot be told apart. The first page of the publicly available PDF now carries the note . The error came from a misreading of the column classifying whether someone is an expert (pointed out by AI Impacts in 2016).
The popular story:“AI is always 15 to 25 years away” is often cited The original source says:The original paper now carries the note . However, the error concerns the classification of experts, and the note does not tell us whether the 15-to-25-year finding itself falls apart
What we still don’t know:Whether predictions cluster around 20 years ahead changes depending on how the data are built. It is not clear.
Tracing a national teaching material's prediction, (translated), back to its source — it began as a line drawn on a supercomputer-speed figure in Kurzweil's 2005 book
Teacher-training material (2020) from the Ministry of Education, Culture, Sports, Science and Technology for the high-school course “Information II” (Japan's high-school informatics course that follows Information I), based on a document from the Ministry of Internal Affairs and Communications' 2014 White Paper on Information and Communications, says this: if computing speed keeps rising as it is, by 2025 it will reach the performance needed to fully simulate (imitate and run inside a computer) one human brain. Tracing the source, the White Paper carried this statement not in its main text but in Figure 3-1-1-4, . The figure's source is a document presented at a Ministry of Internal Affairs and Communications meeting on February 13, 2014 by Mr. Kitani (NTT Data Technology Development Headquarters, according to the document's cover). That document says it was made from a figure in Ray Kurzweil's 2005 book The Singularity Is Near. The original figure plots supercomputer speeds (FLOPS: how many decimal-number calculations per second) as dots, with a straight line (Trendline) that doubles every 1.2 years, and at the point where that line reaches 10¹⁹ FLOPS it carries the note . In other words, the original was not brain simulation itself but a forecast of computing speed.
The popular story:People tend to take it as a prediction that by 2025 the whole human brain can be reproduced on a computer (the headline of the 2014 meeting document also reads “In 2025, simulation of the human brain on a supercomputer becomes possible” (translated)) The original source says:The original figure (Kurzweil 2005) overlays the year when the supercomputer performance trend reaches 10¹⁹ FLOPS (2025) with an estimate that this speed is needed to simulate the nerves of the brain; it does not say that anyone will simulate a whole brain in 2025. The sentence in the national teaching material says (translated), which is written as a forecast of computing speed. Some change of wording can also be seen in the process of translation into Japanese. The original Neural Simulation for Uploading became performance to simulate (translated), and the 10¹⁶ FLOPS became (translated).
What happened next:Checking computing speed: by the same measure as the original figure (the HPL value used in the TOP500 supercomputer performance ranking; the original figure also cites TOP500 as its source), as of November 2025 the leader, El Capitan (USA), is at 1.809 exaflops (about 1.8×10¹⁸ operations per second), only about one fifth (1/5.5) of 10¹⁹ FLOPS. LineShine (China), which took first place in June 2026, is at 2.198 exaflops and has not reached it either. On the other hand, in HPL-MxP (formerly HPL-AI), a different ranking that measures a method mixing in calculations with fewer digits (mixed-precision), three machines passed 10¹⁹ FLOPS in November 2025: El Capitan (16.680), Aurora (11.643) and Frontier (11.390). 10¹⁶ FLOPS (predicted in the figure for 2013) had been reached by Japan's in November 2011 at 10.51 petaflops. Brain simulation results: in 2013, using all the compute nodes of the , a simulation of 1.73 billion nerve cells and 10.4 trillion synapses (about 1% of the human brain's neural circuitry) took 40 minutes to reproduce 1 second of brain activity (RIKEN and others). In 2018, RIKEN wrote that even the highest-performance supercomputer of the time could not simulate a whole human brain, and announced an approach toward achieving it on next-generation supercomputers from 2020 on. In November 2025 the Allen Institute, the University of Electro-Communications and others announced that they had used to simulate in detail the whole cerebral cortex of a mouse (about 10 million nerve cells, 26 billion synapses and 86 brain regions). The Allen Institute's Anton Arkhipov said that the long-term goal is to model the whole brain, and eventually a model of the human brain. None of the announcements from the parties concerned that I opened on this site said that a whole human brain had been simulated by 2025.
What we still don’t know:How much computation is really needed to simulate a whole human brain differs greatly depending on who estimates it. A note in another chapter of the same 2014 White Paper gives a forecast, from IBM's Modha in 2008, that simulating a human brain would become possible in 2018 at 38.5 petaflops (about 4×10¹⁶). That is a gap of about 260 times from Kurzweil's figure of 10¹⁹. The speed needed changes with how finely nerve cells are imitated (for example, the 2025 simulation on was announced as imitating even the flow of electricity inside the branches of nerve cells). This site has not been able to confirm whether there is no example anywhere of a whole human brain being simulated by 2025 (I opened only three announcements from the parties concerned).
What the figure shows:A study reported that AI predictions often looked 15–25 years ahead, but the study itself later received a note about errors. The answer changes with how predictions are collected and counted.
Closing
The Next Page Is Yours to Write
The history of AI is a record of nearly 400 years of challenges by people who dreamed of thinking machines. There were days when the goal came sooner than expected, and days when it was farther than expected. Each time, someone built a new tool, and the next person used it to take one more step ahead.
On this site, we went back to the speaker's own book or paper to check the famous stories. If you touch the figures and rewrite the Python code, you can run the same mechanisms with your own hands. Read freely, starting from whatever chapter caught your interest.
On the map of predictions, many predictions are waiting to be checked. 2030, 2045 and so on. The people who will see those answers come in are you, the high-school students of today. And the people who write the next prediction or the next invention will surely be some of you, too.