Nakayama , Shimojo , and Ramachandran ' s 1990 paper

Surfaces revisited The target paper reviewed in this article was titled `̀ Transparency: relation to depth, subjective contours, luminance, and neon colour spreading'' coauthored by K Nakayama, S Shimojo, and V S Ramachandran, published in 1990. This paper, one of the first in a series on surface perception, examined how in untextured stereograms, local disparity and luminance contrast can drastically change surface quality, subjective contours, and the effect of neon colour spreading. When we began to conceive this and related work, the ascendant view on visual perception was derived from the pioneering studies of the response properties of visual neurons with microelectrodes, including those of Barlow (1953), Lettvin et al (1959), and Hubel and Wiesel (1959, 1962). All suggested that there are remarkable operations on the image by earliest stages of the visual pathway, which bestowed selectivity to colour, orientation, motion direction, spatial frequency, binocular disparity, etc. As such, it would seem that an understanding of vision would come through more systematic description of the properties of single neuron selectivities. This viewpoint was well summarised by Horace Barlow in his famous neuron doctrine paper (Barlow 1972), which emphasised the importance of analysing the image in successive stages of processing by neurons with specific classes of receptive fields. Later work altered this conception somewhat by seeing receptive fields as linear filters. Rather than detecting the presence of edges, bars, or otherwise perceptually identifiable elements in a scene, cells were seen as making measurements of an image. It was an `image based' approach to vision, treating the basic operations of vision with no particular regard as to what aspects of scenes were being coded, whether a given cell's response corresponded to something about surfaces, edges, or objects in the real world. Representing an older and radically different perspective were the views of perceptual psychologists, Irvin Rock and Richard Gregory among others. In the tradition of Helmholtz, they took a more psychological and cognitive view of visual processing, suggesting that visual perception was the result of inference, logic, or reasoning (Rock 1983), or that percepts were hypotheses (Gregory 1966/1997). Perception was a process that led to a real-world understanding of the image. This approach to vision suggested that vision was more akin to higher levels of thinking, not easily described in terms of individual neurons with their characteristic receptive fields. Marr (1980), among others, realised that each of these two rival approaches was incomplete. He attempted a larger synthesis of vision, arguing that it must comprise distinct stages with very different properties. Analysis of the image could take place at early stages of the visual pathway, but later stages required processing that would appear to be more abstract. These stages were important to generate a viewpointdependent representation of surfaces in the world (the 2Ã~Ä -D sketch), which then later stages matched with 3-D models of objects. Our contribution in this and a series of related papers argues for the existence of an intermediate level of representation corresponding to visual surfaces, and to make an attempt to understand it. As evidence, we generated a variety of perceptual demonstrations relying heavily on binocularly presented stimuli to manipulate depth cues without changing the monocular image in obvious ways. Our goal was not to study Perception, 2009, volume 38, pages 859 ^ 877