Among these types it is the physiologists who like to emphasise that their methods are the more fundamental However even if we knew how every nerve cell operated in the performance of some pattern of behaviour this would not remove the need for us to study it at a behavioural level also Behaviour has its own organisation and its own units mat we must use for its study Trying to describe the nestbuilding behaviour of a bird in terms of the actions of individual nerve cells would be like trying to read a page of a book with a highpowered microscope