Marr, David
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Marr was born in Essex in 1945, received his bachelors degree in mathematics (1966) and PhD in physiology (1972) from Trinity College, Cambridge, and died from leukaemia in Cambridge, Massachusetts, in 1980 at the age of 35. Although his career was tragically cut short, his theory of vision remains as probably the most complete account of visual perception, and one of the most influential theories of psychology, ever developed.
His early work in Cambridge, UK, focused on the function of the cerebellum, hippocampus and neocortex, but he is primarily remembered for his work on vision that was completed in Cambridge, US, at the Massachusetts Institute of Technology's (MIT) department of psychology. Marr's approach to vision was characterised by identifying the problems faced by the brain in perceiving the surrounding world and the solutions it finds to overcome these problems. Eschewing general theoretical debates, he embraced Gibson's ideas concerning the wealth of information present in the environment, but believed the solution to perception could be found in how the brain made sense of this information. As such, Marr's is an information processing theory that took a 'bottom-up' approach, as he attempted to map how information flowed from the senses and was made sense of by the brain. The start point was, therefore, the image formed on the retina, and the endpoint were internal representations that could be used to recognise objects encountered in the environment.
Although his theory (published in 1982 in a book titled 'Vision: A Computational Investigation into the Human Representation and Processing of Visual Information') contains a great deal of specific detail as to how exactly information might be processed by the brain, perhaps the most influential aspects were that he proposed three different levels of analysis and that vision occurred in stages. The levels of analysis (often referred to as Marr's tri-level hypothesis) separated the physical level, such as the structure of the brain, from the algorithmic level, the processes, computations and representations used to analyse information, from the computational level, concerned with identifying what problems are solved and how. His stages of vision, which went from the primal sketch to the 2.5D sketch to the 3D model representation, involved building an ever more complex representation based on information present in the initial retinal image.
As well as having a considerable impact on psychological research on visual perception, Marr's theory and approach were also to strongly influence and shape the fields of cognitive science and machine vision; indeed it is hard to underestimate just how significant his theory was or to imagine what modern research on perception would be without it.
Written by: Graham Pike