Animals in Translation by Temple Grandin Page B

brains, the only difference that’s obvious to the naked eye is the increased size of the neocortex in people. (Usually the words “neocortex” and “cerebral cortex” mean the same thing, but some researchers use “neocortex” to mean the newer, six-layered part of the cerebral cortex. I’m using “neocortex” and “cerebral cortex” interchangeably.) The neocortex is the top layer of the brain, and includes the frontal lobes as well as all of the other structures where higher cognitive functions are located.
    The neocortex is wrapped around all the subcortical or lower brain structures, which are the seat of emotions and life support functions in people and animals. In humans the neocortex is so thick compared to the lower brain structures that it’s the size of a peach compared to a peach pit. In animals the cortex is much smaller. It’s so small that in some animals the “peach” is the same size as the “pit” the neocortex is the same size as all the lower brain structures.
    As a general rule, the more intelligent the animal species, the bigger the neocortex. If you remove the neocortex, you can’t tell an animal brain apart from a human brain, just to look at them. I had a hands-on lesson in this in grad school when I dissected a human brain and a pig brain in a class I took at the University of Illinois. The pig brain was a big shock for me, because when I compared the lower-level structures like the amygdala to the same structures in the human brain I couldn’t see any difference at all. The pig brain and the human brain looked exactly alike. But when I looked at the neocortex the difference was huge. The human neocortex is visibly bigger and more folded-up than the animal’s, and anyone can see it. You don’t need a microscope.
    Comparing animal brains to human brains tells us two things.
    Number one: animals and people have different brains, so they experience the world in different ways—
    and
    Number two: animals and people have an awful lot in common.
    To understand why animals seem so different from normal human beings, yet so familiar at the same time, you need to know that the human brain is really three different brains, each one built on top of the previous at three different times in evolutionary history. And here’s the really interesting part: each one of those brains has its own kind of intelligence, its own sense of time and space, its own memory, and its own subjectivity. It’s almost as if we have three different identities inside our heads, not just one.
    The first and oldest brain, which is physically the lowest down inside the skull, is the reptilian brain.
    The next brain, in the middle, is the paleomammalian brain.
    The third and newest brain, highest up inside your head, is the neomammalian brain.
    Roughly speaking, the reptilian brain corresponds to that in lizards and performs basic life support functions like breathing; the paleomammalian brain corresponds to that in mammals and handles emotion; and the neomammalian brain corresponds to that in primates—especially people—and handles reason and language. All animals have some neomammalian brain, but it’s much larger and more important in primates and in people.
    The three brains are connected by nerves, but each one has its own personality and its own control system: the “top” doesn’t control the “bottom.” Researchers used to think that the highest part of the brain was in charge, but they no longer believe this. That means we humans probably really do have an animal nature that’s separate and distinct from our human nature. We have a separate animal nature because we have a separate animal brain inside our heads.
    The reason we have three separate brains instead of just one is that evolution doesn’t throw away things that work. When a structure or a protein or a gene or anything else works well,