Chris Bishop: Even the most sophisticated computers can't tell a dog from a cat

Tuesday 06 January 2009 01:00 GMT

The task of recognising structure or objects in data is called pattern recognition. It's something computers find incredibly difficult. Let's say we want to distinguish between pictures of cats and pictures of dogs. The problem is that there is huge variation in the images. There are different sizes and different colours of cats and dogs, and different shapes, and there are changes in the lighting and changes in the background. Even just working out which part of the image is the animal and which is the background is hard for a computer.

Back in the 1970s, scientists tried creating artificial intelligence using an idea called Expert Systems, which were based on handcrafted rules. The problem is, when we have a rule, we often find there's an exception to the rule – a cat with long fur and a dog with short fur. When we think of a rule, we can often find an exception. So while rule-based systems have been found useful for some applications, we've pretty much given up using them to do pattern recognition.

So what we need is a new approach. The idea is this – instead of programming the computer to solve the pattern recognition problem directly, we programme the computer to learn from data and then we train the computer to solve the problem, a bit like the way you and I learn things from experience.

An adult human is thought to be able to distinguish tens of thousands of categories of objects. Even a toddler is significantly better at recognising everyday objects than a supercomputer. And yet the progress that we've made so far has already led to some practical applications, from allowing robots in factories to see what they're assembling, to allowing tumours to be detected in medical images.

The challenge of digital intelligence is one of the most fascinating frontiers of computer science. It's more than half a century since the first digital computers were built, and yet we're still at the beginning of the digital revolution. Whatever advances the next 50 years bring, they will be at least as important and at least as exciting as those of the past 50, and it's the scientists of the next generation that will make it happen.

From one of the Royal Institution Christmas Lectures by Professor Chris Bishop, Chief Research Scientist at Microsoft Research, Cambridge

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