Optic flow provides all the information necessary to guide a walking human or a mobile robot to its target. Over the past 50 years, a body of research on optic flow spanning the disciplines of neurophysiology, psychophysics, experimental psychology, brain imaging and computational modelling has accumulated. Today, when we survey the field, we find independent lines of research have now converged and many arguments have been resolved; simultaneously the underpinning assumptions of flow theory are being questioned and alternative accounts of the visual guidance of locomotion proposed. At this...

Communication is one of the most challenging human phenomena, and the same is true of its paradigmatic verbal realization as a dialogue. Not only is communication crucial for virtually all interpersonal relations; dialogue is often seen as offering us also a paradigm for important intra-individual processes. The best known example is undoubtedly the idea of concep tualizing thinking as an internal dialogue, "inward dialogue carried on by the mind within itself without spoken sound," as Plato called it in the Sophist. At first, the study of communication seems to be too vaguely defmed to have...

In the late 1960s and early 1970s David Marr produced three astonishing papers in which he gave a detailed account of how the fine structure and known cell types of the cerebellum, hippocampus and neocortex perform the functions that they do. Marr went on to become one of the main founders of Computational Neuroscience. In his classic work 'Vision' he distinguished between the computational, algorithmic, and implementational levels, and the three early theories concerned implementation. However, they were produced when Neuroscience was in its infancy.
Now that so much more is known, it is...