This week's programme in the series on Man and Science Today.

Patient: "My head aches"
Doctor: "Tell me more about your pains in general"
Patient: "My stomach bothers me, too"
Doctor: "Do you see any relationship between your head and your stomach pain?"
A fairly conventional start to a conversation between a patient and his doctor. In this case, though, the doctor was a computer.
Equally conventional was the start of a chess game in Boston, Mass., recently in which Benjamin Landy, a respected tournament player, was beaten by MacHack, another computer. Landy's game was described as 'a chess periodical-' and 'a disgrace to the human race.' Tonight we watch the return match - the outcome is again uncertain as both man and computer have improved.
Once, machines copied only man's physical activities - now they can mimic many of his mental processes. How long before they can design their own 'intelligent' programmes, how long before they become man's intellectual superior?
These questions, posed in tonight's Horizon, no longer have the hollow ring of fantasy. There may be many problems before any machine matches HAL in the film 2001, but so far, scientists can see no limitations to the growth of machine intelligence.