
IN December, philosopher and artificial intelligence expert announced his intention to create nothing less than a robot mathematician. He reckons he has identified a key component of how humans develop mathematical talent. If he鈥檚 right, it should be possible to program a machine to be as good as us at mathematics, and possibly better.
This is no mad quest, insists Sloman, of the University of Birmingham in the UK. 鈥淗uman brains don鈥檛 work by magic, so whatever it is they do should be doable in suitably designed machines,鈥 he says.
鈥淗uman brains don鈥檛 work by magic, so whatever it is they do should be doable by machine鈥
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Sloman鈥檚 creature is not meant to be a mathematical genius capable of advancing the frontiers of mathematical knowledge: his primary aim, outlined in the journal , is to use such a machine to improve our understanding of where our mathematical ability comes from. Nevertheless, it is possible that such a robot could take us beyond what mathematicians have achieved so far. Forget robot vacuum cleaners and android waitresses; we鈥檙e talking about a machine that could spawn a race of cyber-nerds capable of creating entirely new forms of mathematics.
The field of artificial intelligence has promised much before, of course. Early researchers thought it might open a fast-track to understanding consciousness, and there were claims that artificially intelligent computers and robots would change the world. The truth has been more prosaic. AI has done some clever things, such as give us great chess players and voice recognition software, but it hasn鈥檛 delivered a revolution.
But when it comes to mathematics, we can鈥檛 rule one out yet, says , who researches the philosophy of mathematics at the University of Edinburgh, UK. Pease teaches computers to do mathematics using AI programs, and thinks a computer really could astonish its programmer with a new mathematical insight. 鈥淥urs hasn鈥檛 yet, but there is no reason why one shouldn鈥檛 in the future,鈥 she says.
The first concrete step towards this scenario came with a program written by Simon Colton, now at Imperial College London. The program was named , in honour of the mathematicians Godfrey Harold Hardy and Srinivasa Ramanujan. It looked for 鈥渋nteresting鈥 sequences of numbers (快猫短视频, 24 February 2001, p 13).
Some of HR鈥檚 discoveries have even been published 鈥 and HR, rather than Colton, got the credit. Though they might not look like cutting-edge advances, they could yet prove important. 鈥淚 always refer to HR鈥檚 work in number theory as recreational mathematics, but things that look insignificant can end up being hugely significant and interesting,鈥 Colton says.
Pease and her colleagues Alan Smaille and Markus Guhe have recently taken things further. In their Edinburgh computing laboratory they have been running virtual mathematics conferences, populated entirely by digital mathematicians (see 鈥淩einventing the conjecture鈥). So where might that lead?
All the way to significant new mathematics, Sloman hopes. His idea is that our key mathematical capabilities are formed in childhood. So rather than engineering a fully fledged mathematician鈥檚 brain, Sloman thinks we should build a robot with a child-like brain and let it grow into its mathematical destiny.
There鈥檚 just one problem. How do we know which of our childhood capabilities equip us for a life of juggling numbers?
Sloman is busy gathering clues. The answer, he reckons, lies in the spatial awareness skills that children must acquire in order to negotiate their world: skills such as knowing that a toy train pushed into a tunnel will come out the other side. Or that a jigsaw puzzle piece fits its gap only when correctly oriented. Or that the number of toys on the sofa does not depend on the order in which you count them.
From the minds of babes
You might be surprised to learn, for instance, that you grasped the topological concept called 鈥渢he transitivity of containment鈥 when you were still a toddler. Stacking cups, one inside the other, you learned that the small cup would fit not only in the medium-sized cup, but also inside the big one.
Transitivity of containment, like other geometrical and topological concepts, is learned through experience. 鈥淭here are hundreds, if not thousands more examples of things a child learns empirically, that are later seen to be theorems in topology, geometry and arithmetic,鈥 Sloman says.
At some point, children make that jump for themselves. As toddlers, we soon translate our experiences into general theorems which we use to make predictions.
Take the train-through-a-tunnel example. By repeated experiences like this, toddlers learn the basic properties of rigid rods. That鈥檚 why a 3-year-old carrying a long broom handle can negotiate a narrow corridor, turn a corner at the end without getting the broom handle caught in the vertical bars of a stair-gate, then make adjustments so that the handle will go through the next doorway. 鈥淭here is a switch from learning empirically to realising it has 鈥榮imply got to be like that鈥,鈥 Sloman says.
And here is the key to the emergence of the mathematical mind. 鈥淭he mechanisms that make that possible in a child are related to what makes it possible for them to go on to become a mathematician,鈥 Sloman says. 鈥淎 lot of abstract maths has its roots in our ability to think about space and time, processes, and interactions between processes and structures.鈥
Sloman has gone back to basics, to watch how children learn to navigate the world around them. He is building an archive of observations of children performing pseudo-mathematical tasks. These navigational and object manipulation skills 鈥 or at least the ability to acquire them quickly 鈥 must be encoded in the genome, Sloman reckons. And that means they could be encoded in a machine.
Sloman is still a long way from designing his robot toddler. Once he has catalogued the abilities of children at various stages of development, he still has to work out how to understand the mathematical implications of those abilities, then represent them in some form of computer code. 鈥淚nformation needs to be encoded in some form in order to be usable,鈥 he says. The gargantuan scale of the task means his aims are necessarily modest: at this stage he is simply trying to show a link between spatial manipulations and the basics of mathematics. Anything more would be a bonus. But just how big could that bonus be? Could a robot mathematician really do something interesting?
鈥淚n principle, yes, absolutely,鈥 Pease says. But, she adds, the story-so-far tempers her optimism. 鈥淥f all the scientific and mathematical discovery programs I鈥檝e looked at, nothing has yet made a big discovery.鈥 At the very least, she says, that means there is a long way to go.
Colton thinks there is every reason to believe computers could produce something interesting to mathematicians. 鈥淪oftware is already producing theorems of value to maths,鈥 he points out. 鈥淣ot of huge value, I admit 鈥 but then the average student or mathematician isn鈥檛 producing anything of huge value either.鈥
He and his team are convinced that computers can be genuinely creative. 鈥淐reativity is a very loaded word: people like to think it鈥檚 a uniquely human attribute,鈥 he says. 鈥淭he fact is, computers doing maths are more likely to be creative than, say, an undergraduate student, in many ways.鈥
Others are sceptical of this view. Computers are a useful tool, says an expert on mathematical cognition at the University of California, San Diego, but the sense that computers can invent mathematics is an illusion. Though it looks like we can make progress by programming machines to do mathematics, he reckons there can be nothing in these machines that isn鈥檛 pre-ordained by human mathematical concepts. 鈥淔or me, it鈥檚 like computing the decimal places of pi,鈥 N煤帽ez says. 鈥淥nce we have decided what the right rules are, we鈥檙e just using the computer to crunch numbers.鈥
Sloman thinks N煤帽ez鈥檚 view is too narrow. He points to 鈥渆volutionary algorithms鈥 as a reason for optimism. This innovation allows a computer to evolve its own programs by producing lots of them, testing them against a goal criteria, and then selecting and 鈥渋nterbreeding鈥 the best ones. It has allowed computers do things that nobody programmed them to do. 鈥淚n some cases no human even knows how they do what they do,鈥 Sloman says. Aerospace and automobile designers have been using evolutionary algorithms since the late 1980s to optimise aircraft parts and streamline their designs. Even city traders are using them to buy and sell shares (快猫短视频, 28 July 2007, p 26).
Evolution has a few million years head start on us in developing brilliant mathematicians, of course, but at least we鈥檙e now in the race. 鈥淥ur big discovery would be how do we do mathematics, rather than how do we write a program that can generate really new mathematics,鈥 says Pease. 鈥淏ut hopefully one would lead on from the other.鈥
Reinventing the conjecture
The traditional view of mathematics sees it as a set of some eternally existing rules that describe the universe. Doing maths involves exploring this abstract, ethereal domain.
Though appealing to many, this notion of mathematicians as intrepid explorers is nothing more than a romantic myth, according to Alison Pease of the University of Edinburgh, UK. 鈥淢aths is not discovery,鈥 she says. 鈥淚t鈥檚 a thing that we invent.鈥
It is something that her computers can invent too, she insists. Pease runs an AI program called , which puts together 鈥渁gents鈥 in a student-teacher relationship.
The students are programmed to take some input information, make inferences from it and try to assess just how 鈥渋nteresting鈥 those inferences are. If sufficiently interesting, the teacher gets involved, calling a group brainstorm designed to develop the ideas further.
One of HRL鈥檚 early successes was the independent invention of a mathematical proposition called Goldbach鈥檚 conjecture. One of the students was given the concept of integers and divisors, and instructed to use these to play around with the integers 1 to 10, looking for interesting relationships. A second student had the same concepts and instructions, but played with the integers 11 to 20.
Student two generated two new concepts: 鈥渆ven numbers鈥 and 鈥渢he sum of two primes鈥. Then it generated a conjecture: that all even numbers can be expressed as the sum of two primes. It thought this was interesting, and sent its work to the teacher to be placed on the agenda for discussion.
The response was positive. 鈥淭he teacher sent a request for modifications to this conjecture, and student one found the counterexample,鈥 Pease says. That counterexample is the number 2: the conjecture was modified to 鈥渁ll even numbers except 2 are the sum of two primes鈥.
The fact that Christian Goldbach came up with this still unproven conjecture in 1742 makes it a little less impressive, but the point is made. Even if computers are a few centuries behind, it seems that machines really can do what human mathematicians do.