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

Revenge of the Nerds 191WHY US?Why did some miocene ape first enter the cognitive niche? Why not agroundhog, or a catfish, or a tapeworm? It only happened once, so noone knows. But I would guess that our ancestors had four traits thatmade it especially easy and worth their while to evolve better powers ofcausal reasoning.First, primates are visual animals. In monkeys such as the rhesusmacaque, half the brain is dedicated to sight. Stereoscopic vision, theuse of differences in the vantage points of the two eyes to give a sense ofdepth, developed early in the primate lineage, allowing early nocturnalprimates to move among treacherous fine branches and to grab insectswith their hands. Color vision accompanied the switch of the ancestorsof monkeys and apes to the day shift and their new taste for fruits, whichadvertise their ripeness with gaudy hues.Why would the vision thing make such a difference? Depth perceptiondefines a three-dimensional space filled with movable solid objects.Color makes objects pop out from their backgrounds, and gives us a sensationthat corresponds to the stuff an object is made of, distinct fromour perception of the shape of the stuff. Together they have pushed theprimate brain into splitting the flow of visual information into twostreams: a "what" system, for objects and their shapes and compositions,and a "where" system, for their locations and motions. It can't be a coincidencethat the human mind grasps the world—even the most abstract,ethereal concepts—as a space filled with movable things and stuff (seeChapters 4 and 5). We say that John went from being sick to being well,even if he didn't move an inch; he could have been in bed the wholetime. Mary can give him many pieces of advice, even if they merely talkedon the phone and nothing changed hands. Even scientists, when they tryto grasp abstract mathematical relationships, plot them in graphs thatshow them as two- and three-dimensional shapes. Our capacity forabstract thought has co-opted the coordinate system and inventory ofobjects made available by a well-developed visual system.It is harder to see how a standard mammal could have moved in thatdirection. Most mammals hug the ground sniffing the rich chemicaltracks and trails left behind by other living things. Anyone who has