Although the study of visual perception has made more progress in the past 40 years than any other area of cognitive science, there remain major disagreements as to how closely vision is tied to general cognition. This paper sets out some of the arguments for both sides and defends the position that an important part of visual perception, which may be called early vision or just vision, is prohibited from accessing relevant expectations, knowledge and utilities - in other words it (...) is cognitively impenetrable. That part of vision is complex and articulated and provides a representation of the 3-D surfaces of objects sufficient to serve as an index into memory, with somewhat different outputs being made available to other systems such as those dealing with motor control. The paper also addresses certain conceptual and methodological issues, including the use of signal detection theory and event-related potentials to assess cognitive penetration of vision. A distinction is made among several stages in visual processing. These include, in addition to the inflexible early-vision stage, a pre-perceptual attention allocation stage and a post-perceptual evaluation, memory-accessing, and inference stage which provide several different highly constrained ways in which cognition can affect the outcome of visual perception. The paper discusses arguments that have been presented in both computer vision and psychology showing that vision is "intelligent" and involves elements of problem solving". It is suggested that these cases do not show cognitive penetration, but rather they show that certain natural constraints on interpretation, concerned primarily with optical and geometrical properties of the world, have been compiled into the visual system. The paper also examines a number of examples where instructions and "hints" are alleged to affect. (shrink)

If a man born blind were to gain his sight in later life would he be able to identify the objects he saw around him? Would he recognise a cube and a globe on the basis of his earlier tactile experiences alone? This was William Molyneux's famous question to John Locke and it was much discussed by English and French empiricists in the eighteenth century as part of the controversy over innatism and abstract ideas. Dr Morgan examines the whole history (...) of this debate: Locke's own (negative) answer to the question, the contributions of Berkeley, Condillac, Diderot and Voltaire and the factual accounts of early cataract operations and modern laboratory studies. He shows how this debate is involved in the development and eventual separation of philosophy and experimental psychology after the eighteenth century and considers why the original question is effectively still unanswered. This is one problem-area with its intricate cluster of connected conceptual and technical difficulties which suggests the need for some reunion or at least collaboration between the two subjects. (shrink)

Although the mechanics of how the eye works are well understood, debate still exists as to how the complex machinery of the brain interprets neural impulses...