Our versatile minds enable us to think how a murder can be committed when the killer is on a train and the victim is in a cinema. Yet we often forget verbal directions telling us how to get from one place to another. In the first of three conversations about language and thought, Professor Colin Blakemore discusses with Dr Philip Johnson-Laird , of the Medical Research Council's Applied Psychology Unit in Cambridge, how he combines such evidence with theories of artificial intelligence to understand how we reason. Producer DEBORAH COHEN (R) revised