Relating cognitive psychology to neurobiology helps us to understand how autism and its variants arise. A confluence of neuroanatomical, neurophysiological, and genetic data suggests that the brains of people with autism spectrum conditions may differ from normal in terms of the balance between local and long-range neural connectivity: in the autistic brain, neurones may communicate very much with their neighbours within the same brain region, but only weakly with neurones in distant brain regions. This neural abnormality in connecting separate brain regions gives rise to a cognitive abnormality in connecting separate elements of perceptual and cognitive experience – a property that has been labelled `weak central coherence' and which gives rise to characteristic patterns of cognitive deficits and cognitive skills. Autism's sensory and cognitive worlds therefore are experienced in a way that is more direct and less buffered, more piecemeal and less narratively coherent, than the experience of the normal brain. Psychologically, autistic behaviour can be most productively construed as the developmental response of a rational human mind to this abnormal perceptual and cognitive environment.