Computers are extraordinary machines, able to perform feats of arithmetic that far exceed the capabilities of any human. They can store a huge quantity of data and recall it perfectly in the blink of an eye. They can even beat the chess world champion at his own game. So why do computers struggle to solve apparently simple tasks such as understanding speech, or translating text between languages? Why is a three-year-old child better at recognising everyday objects than the world’s most powerful supercomputer? In the last of this year’s lectures, Chris Bishop looks at one of the great frontiers of computer science. He explains how some of the toughest computational problems are now being tackled by giving computers the ability to learn solutions for themselves. This has led to impressive progress with problems such as recognising handwriting and finding information on the web. Scientists are particularly concerned with the area of computer vision – the technology of making computers see what is placed in front of them. If perfected, this ability could be applied to all manner of practical uses, from medical scanners to cars that run on autopilot. However, exactly what constitutes intelligence remains an area of much philosophical debate. It can include skills such as logic, linguistic ability, spatial awareness, musical talent and inter personal skills. For many scientists, it remains to be seen how many of these abilities – if any – can be successfully developed in computers, and whether digital intelligence is even comparable to its human equivalent. There are many challenges ahead in the quest to build the ultimate computer.