Steven Pinker -- How the Mind Works - Hampshire High Italian ...

260 | HOW THE MIND WORKSWe perceive surfaces involuntarily, impelled by information surging upfrom our retinas; contrary to popular belief, we do not see what weexpect to see.So what is the product of vision? Marr called it a 2V2-D sketch; otherscall it a visible surface representation. Depth is whimsically downgradedto half a dimension because it does not define the medium in whichvisual information is held (unlike the left-right and high-low dimensions);it is just a piece of information held in that medium. Think of thetoy made of hundreds of sliding pins which you press against a 3-D surface(such as a face), forming a template of the surface in the contour ofthe pins on the other side. The contour has three dimensions, but theyare not created equal. Position from side to side and position from top tobottom are defined by particular pins; position in depth is defined byhow far a pin protrudes. For any depth there may be many pins; for anypin there is only one depth.The 2'/2-D sketch looks a bit like this:It is a mosaic of cells or pixels, each dedicated to a line of sight from thecyclopean eye's vantage point. It is wider than it is tall because our twoeyes sit side by side in our skulls rather than one being above the other.The cells are smaller in the center of the visual field than in the peripherybecause our resolution is greater in the center. Each cell can representinformation about a surface or about an edge, as if it had two kinds