Production systems in artificial intelligence are a way of representing the mental processing that may take place when people solve problems. We look in this programme at the operation of a simple ...production system for a cooking task and compare the use of such a system to a more conventional flow chart. Then we see in some detail how a production system can represent the changing approach of a child to solving a simple problem as he develops mentally. This programme was also recorded at Edinburgh University with the help of a participating audience.