Excerpted from Animals in Translation: Using the Mysteries of Autism to Decode Animal Behavior by Temple Grandin and Catherine Johnson. © 2004 by Temple Grandin and Catherine Johnson. Published by Scribner. Reprinted with permission.
LIZARD BRAINS, DOG BRAINS, AND PEOPLE BRAINS
When you compare human and animal 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—
Number two: animals and people have an awful lot in common.
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.
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, nature uses it again and again in newly evolved plants and animals. The word for this is conservation. Biologists say that evolution conserves structures that work.
Paul MacLean, the originator of the three-brain theory, believes that evolution simply added each newly evolved brain on top of the one that came before, without changing the older brain. He calls this the triune brain theory.
In other words, if you’re Mother Nature, and you’ve got a lot of lizards running around the world breathing, eating, sleeping, and waking up just ﬁne, you don’t create a whole brand-new dog breathing system when it comes time to evolve a dog. Instead, you add the new dog brain on top of the old lizard brain. The lizard brain breathes, eats, and sleeps; the dog brain forms dominance hierarchies and rears its young.
The same thing happens all over again when nature evolves a human. The human brain gets added on top of the dog brain. So you have your lizard brain to breathe and sleep, your dog brain to form wolf packs, and your human brain to write books about it. In a lot of ways evolution is like building an addition onto your house instead of tearing down the old one and building a new one from the ground up.
TRAPPED INSIDE THE BIG PICTURE
What the neocortex does better than the dog brain or the lizard brain is tie everything together. The whole neocortex is one big association cortex, making connections between all kinds of things that stay more separate for animals. For instance, take the fact that humans have mixed emotions. A human can love and hate the same person. Animals don’t do that. Their emotions are simpler and cleaner, because categories like love and hate stay separate in their brains.
Another example: humans make rapid generalizations from one situation to another; animals don’t. A generalization depends on making an association between one situation or object and another, similar situation or object. Compared to humans, animals generalize so little that one of the most important aspects of any animal training program is getting the animal to make a generalization from the training situation to the rest of his life. A dog can learn to perform tasks at a training school and not know how to perform them at home, because school and home are separate categories. His brain doesn’t automatically associate the two. I’ll talk about this more in other chapters.
Humans make rapid generalizations from one situation to another; animals don’t. A generalization depends on making an association between one situation or object and another, similar situation or object. Compared to humans, animals generalize so little that one of the most important aspects of any animal training program is getting the animal to make a generalization from the training situation to the rest of his life.
Inside the neocortex, the frontal lobes, which sit behind your forehead, are the ﬁnal destination for all the information that’s ﬂoating around your brain. They pull everything together.
Although growing a big neocortex gave us our “book smarts,” we paid a price. For one thing, bigger frontal lobes probably made humans a lot more vulnerable to brain damage and dysfunction of just about any kind. I wonder whether this explains why you don’t often see animals with developmental disabilities. Estimates of the incidence of mental retardation range from 1 percent of the U.S. population up to as high as 3 percent, and it doesn’t seem like there’s anywhere near that level in animals. It’s possible we humans don’t know what a developmental disability in an animal looks like, but I also question whether animals might be less vulnerable to developmental disabilities in the ﬁrst place because their frontal lobes are less developed.
Frontal lobe functions are the ﬁrst to go, whether the problem is a traumatic head injury, a developmental disability, old age, or just plain lack of sleep. Worse yet, if you damage any part of your brain in an accident or a stroke you wind up with frontal lobe problems even when your frontal lobes weren’t touched.
People always thought this was because the last structure to evolve is the most delicate, while the older structures have been around so long they’ve become incredibly robust. But a neuropsychologist named Elkhonon Goldberg at New York University School of Medicine, who wrote a fantastic book about frontal lobe functions called The Executive Brain, has a different theory. He thinks that while the frontal lobes may be more fragile, there is another factor involved, which is that every other part of the brain is connected to them. When you damage any part of the brain, you change input to the frontal lobes, and when you change input, you change output. If the frontal lobes aren’t getting the right input, they don’t produce the right output even though structurally they’re ﬁne. So all brain damage ends up looking like frontal lobe damage, whether the frontal lobes were injured or not.
I think he’s right about this, because frontal lobe problems are a big part of autism, and our frontal lobes are structurally pretty good. A major autism researcher told a journalist friend of mine that if you compared the brain scan of an autistic child to the scan of a sixty-year-old CEO, the autistic child’s brain would look better. In other words, the normal brain shrinkage people experience with age makes your brain look more “abnormal” than autism does. There are some structural differences between autistic brains and normal brains, but they’re so small you can’t see them on a regular MRI, and probably every person has structural brain differences to that degree.
Of course, the fact that a brain difference is tiny doesn’t mean its effect is tiny. The researcher also said that a brain difference could be subtle but signiﬁcant. But he added that there’s nothing about the anatomy of the autistic brain that told him autism can’t eventually be treated by medication the same way psychiatric disorders can be treated.
Until we learn more, I am assuming that one of the problems in autism isn’t bad frontal lobes; it’s bad input into the frontal lobes.
Bad input can happen to normal people, too. Just being incredibly tired and sleep-deprived will lower your frontal lobe function, and the aging process hurts the frontal lobes much more than any other part of the brain.
That brings me back to animals. The good news is: when your frontal lobes are down, you have your animal brain to fall back on. That’s exactly what happens, too. The animal brain is the default position for people. That’s why animals seem so much like people in so many ways: they are like people. And people are like animals, especially when their frontal lobes aren’t working up to par.
I think that’s also the reason for the special connection autistic people like me have to animals. Autistic people’s frontal lobes almost never work as well as normal people’s do, so our brain function ends up being somewhere in between human and animal. We use our animal brains more than normal people do, because we have to. We don’t have any choice. Autistic people are closer to animals than normal people are.
The price human beings pay for having such big, fat frontal lobes is that normal people become oblivious in a way animals and autistic people aren’t. Normal people stop seeing the details that make up the big picture and see only the big picture instead. That’s what your frontal lobes do for you: they give you the big picture. Animals see all the tiny little details that go into the picture.
EXTREME PERCEPTION: THE MYSTERY OF JANE’S CAT
Compared to humans, animals have astonishing abilities to perceive things in the world. They have extreme perception. Their sensory worlds are so much richer than ours it’s almost as if we’re deaf and blind.
That’s probably why a lot of people think animals have ESP. Animals have such incredible abilities to perceive things we can’t that the only explanation we can come up with is extrasensory perception. There’s even a scientist in England who’s written books about animals having ESP. But they don’t have ESP, they just have a super-sensitive sensory apparatus.
Take the cat who knows when its owner is coming home. My friend Jane, who lives in a city apartment, has a cat who always knows when she’s on her way home. Jane’s husband works at home, and ﬁve minutes before Jane comes home he’ll see the cat go to the door, sit down, and wait. Since Jane doesn’t come home at the same time every day, the cat isn’t going by its sense of time, although animals also have an incredible sense of time. Sigmund Freud used to have his dog with him every time he saw a patient, and he never had to look at his watch to tell when the session was over. The dog always let him know. Parents tell me autistic kids do the same thing. The only explanation Jane and her husband could come up with was ESP. The cat must have been picking up Jane’s I’m-coming-home-now thoughts.
Jane asked me to ﬁgure out how her cat could predict her arrival. Since I’ve never seen Jane’s apartment I used my mother’s New York City apartment as a model for solving the mystery. In my imagination I watched my mother’s gray Persian cat walk around the apartment and look out the window. Possibly the cat could see Jane walking down the street. Even though he would not be able to see Jane’s face from the twelfth ﬂoor he would probably be able to recognize her body language. Animals are very sensitive to body language. The cat would probably be able to recognize Jane’s walk.
Next I thought about sound cues. Since I am a visual thinker I used “videos” in my imagination to move the cat around in the apartment to determine how it could be getting sound cues that Jane would be arriving a few minutes later. In my mind’s eye I positioned the cat with its ear next to the crack between the door and the door frame. I thought maybe he could hear Jane’s voice on the elevator. But as I played a tape of my mother getting onto the elevator in the lobby, I realized that there would be many days when Mother would ride the elevator alone and silent. She would speak on the elevator for only some of the trips—when there were other people in the elevator car with her—but not all of them.
So I asked Jane, “Is the cat always at the door, or is he at the door only sometimes?”
She said the cat is always at the door.
That meant the cat had to be hearing Jane’s voice on the elevator every day. After I questioned her some more, Jane ﬁnally gave me the crucial piece of information that solved the cat mystery: her building does not have a push-button elevator. The elevator is operated by a person. So when Jane got on the elevator she probably said “Hi” to the operator.
A new image ﬂashed into my head. I created an elevator with an operator for my mother’s building. To make the image I used the same method people use in computer graphics. I pulled an image of my mother’s elevator out of memory and combined it with an image of the elevator operator I saw one time at the Ritz in Boston. He had white gloves and a black tuxedo. I lifted the brass elevator control panel and its tuxedoed operator from my Ritz memory ﬁle and placed them inside my mother’s elevator.
That was the answer. The fact that Jane’s building had an elevator operator provided the cat with the sound of Jane’s voice while Jane was still down on the ﬁrst ﬂoor. That’s why the cat went to the door to wait. The cat wasn’t predicting Jane’s arrival; for the cat Jane was already home.
DIFFERENT SENSE ORGANS
Cats have really good hearing, so Jane’s cat was using a sensory capacity we humans don’t have. Animals have all kinds of sensory abilities we don’t have, and vice versa. (Our color vision is a good example of a sensory capacity we have that a lot of animals don’t.) Dogs can hear dog whistles; bats and dolphins can use sonar to “see” a moving object at a distance (a ﬂying bat can actually spot and classify a ﬂying beetle from thirty feet away); dung beetles can perceive the polarization of moonlight. I know dung beetles are insects, not animals, but an insect’s brain is so tiny it makes the things their sensory system can handle even more miraculous.
There are two things going on with extreme perception in animals: one is the different set of sense organs animals have, and the other is a different way of processing sense data in the brain. With Jane’s cat, I’m talking mostly about a different physical capacity to hear sounds humans can’t.
There are hundreds or maybe even thousands of examples of this in the animal world, lots of which we probably still don’t know about. A good example is the silent thunder of elephants. It wasn’t until the 1980s that a researcher named Katy Payne, of Cornell University, ﬁgured out that elephants communicate with one another using infrasonic sound waves too low for humans to hear. People who studied elephants had always wondered how elephant families managed to coordinate their movements with family members miles away. An elephant family could be split up for weeks, and then meet up at the same place at the same time. They had to be communicating with one another somehow, but they were way out of the range any human could either see or shout across.
Katy Payne made a lucky guess about infrasonic sound when she felt “a throbbing in the air” next to the elephant cages at the Portland Zoo in Oregon. She’d had the same feeling as a child when the organ played in church. She started to think maybe the elephants were communicating with each other in a super-low range humans don’t hear. That would solve the problem of the long-distance communication, because infrasonic sound travels a lot farther than sound waves in the register humans do hear.
She turned out to be right. Elephants “roar” out to each other below our level of hearing. During the daytime an elephant can hear another elephant calling him from at least as far away as two and a half miles. At nighttime, because of temperature inversions, that distance can go up by an order of magnitude to as much as twenty-ﬁve miles. It’s a huge distance.
Now it turns out that elephants may be talking to one another through the ground, not just the air. Caitlin O’Connell-Rodwell, a biologist at Stanford, is working on this. She believes elephants can probably use seismic communication—making the ground rumble by stomping on it—to communicate with other elephants as far away as twenty miles.
She ﬁgured this out by watching the elephants in the Etosha National Park in Namibia. Right before another herd of elephants arrived, the elephants she was watching would start to “pay a lot of attention to the ground with their feet.” They’d do things like shift their weight or lean forward, or lift a foot off the ground. They were listening.
Dr. O’Connell-Rodwell thinks the animals are probably using the pads of their feet like the head of a drum. She and her team are also dissecting elephant feet to see whether they have pascinian and meissner corpuscles, which are special sensors elephants have in their trunks to detect vibrations. If they ﬁnd them in the feet, too, that’s pretty good evidence elephants use seismic waves to communicate. A lot of animals communicate by thumping on the ground, including skunks and rabbits, so it won’t surprise me if we ﬁnd out elephants are talking to one another that way.
If elephants do have special corpuscles to detect vibrations that would be an example of an animal species having extreme perception because they’re built differently and have different sense organs. Animals have all kinds of sense receptors we don’t.
If elephants do have special corpuscles to detect vibrations that would be an example of an animal species having extreme perception because they’re built differently and have different sense organs. Animals have all kinds of sense receptors we don’t. Another example: dolphins have an oil-ﬁlled sac in their foreheads, underneath their forehead bumps, that they use for sonar. The dolphin sends a sound through the oil (which “focuses” the sound) and out to objects in the water. The sound bounces back to the dolphin and his brain forms a sound picture of what’s out there. Humans can’t use sonar because humans don’t have any of the necessary sense structures.
Humans also have sensory receptors animals don’t, like the huge number of cones in our retina for seeing color.
I’ve been talking mostly about vision, but all the other senses are different in different animals, too. There’s some fascinating new research about the relationship between vision and smell in New World versus Old World primates. Old World primates are the famous ones everyone knows about: gorillas, chimpanzees, baboons, orangutans, macaques, humans. New World primates are the smaller animals we call monkeys. New World primates usually live in trees in Central and South America; they have long prehensile tails and ﬂat noses. Tamarins, squirrel monkeys, sakis, and marmosets are all New World monkeys.
Old World primates, like baboons, chimpanzees, and macaques, have trichromatic, three-color vision, but most of the New World monkeys (spider monkeys, marmosets, capuchins) only have dichromatic, two-color vision. (Some New World females have trichromatic vision, but not all.)
What’s interesting about this is that Old World primates and humans also have very poor ability to smell pheromones, which are chemical signals animals emit as a form of communication. (Most people think of pheromones as sexual signals, like the pheromones a female in heat emits, but a pheromone is any chemical used for communication. Ants, for instance, leave trails of scents behind them for other ants to follow.) About a year ago researchers found that Old World primates and humans both have so many mutations in a gene called TRP2, which is part of the pheromone signaling pathway, that it’s not working anymore. In the course of evolution, the pheromone system in Old World primates, including humans, broke down.
It turns out that when we gained three-color vision we probably lost pheromone signaling. Jianzhi George Zhang, an evolutionary biologist at the University of Michigan, ran a computer simulation to ﬁnd out when the TRP2 gene started to deteriorate, and discovered that TRP2 went into decline at the same time Old World primates were developing trichromatic color vision, around 23 million years ago.
Probably what happened was that once Old World primates could see in three colors they started using their vision to ﬁnd a mate, instead of their sense of smell. That theory ﬁts with the fact that a lot of Old World primate females have bright red sexual swellings when they’re fertile, while New World monkeys do not. Once monkeys no longer needed a good sense of smell to reproduce successfully, their ability to smell probably went into decline as a direct result.
That would have happened because use it or lose it is a principle in evolution. If monkeys with a poor sense of smell can reproduce just as well as monkeys with an excellent sense of smell, the monkeys with the poor ability pass all of their weak or defective smell genes on to their offspring, and any spontaneous new mutations in the smell genes don’t get winnowed out. It looks like that’s what happened to Old World primates. The normal mutations that happen in the process of reproduction just kept accumulating until no primates had a working copy of TRP2 anymore. Improved vision came at a cost to their sense of smell.
SAME BRAIN CELLS, DIFFERENT PROCESSING
So far I’ve been talking about the sense organ or sense receptor part of animal perception: animals have different sensory organs than we do, organs that let them see, hear, and smell things we can’t. But the other half of the story is where things get interesting, and that is the differences in brain processing.
All sensory data, in any creature, has to be processed by the brain. And when you get down to the level of brain cells, or neurons, humans have the same neurons animals do. We’re using them differently, but the cells are the same.
That means that theoretically we could have extreme perceptions the way animals do if we ﬁgured out how to use the sensory processing cells in our brains the way animals do. I think this is more than a theory; I think there are people who already do use their sense neurons the way animals do. My student Holly, who is severely dyslexic, has such acute auditory perception that she can actually hear radios that aren’t turned on. All appliances that are plugged in continue to draw power, even when they’re turned off. Holly can hear the tiny little transmissions a turned-off radio is receiving. She’ll say, “NPR is doing a show on lions,” and we’ll turn the radio on and sure enough: NPR is doing a show on lions. Holly can hear it. She can hear the hum of electric wires in the wall. And she’s incredible with animals. She can tell what they’re feeling from the tiniest variations in their breathing; she can hear changes the rest of us can’t.
Autistic people almost always have excruciating sound sensitivities. The only way I can describe how a lot of sounds affect me is to compare it to staring straight into the sun. I get overwhelmed by normal sounds in the environment, and it’s painful. Most autism professionals talk about this as just being super-sensitive, which is true as far as it goes. But I think autistic people are also super-perceptive. They’re hearing things normal people aren’t, like a piece of candy being unwrapped in the next room.
It happens with vision, too; a lot of autistic people have told me they can see the ﬂicker in ﬂuorescent lighting. Holly’s the same way. She can barely function in ﬂuorescent lighting because of it. Our whole environment is built to the speciﬁcations and limitations of a normal human perceptual system—and that’s not the same thing as a normal animal perceptual system, or as a normal-abnormal human system like a dyslexic person’s system, or an autistic person’s. There are probably huge numbers of people who don’t ﬁt the normal environment. Even worse, half the time they probably don’t even realize they don’t ﬁt, because this is the only environment they’ve ever been in, so they don’t have a point of comparison.
Some researchers say that people like Holly have developed super-sensitive hearing because their visual processing is so scrambled. Super-sensitive hearing is a compensation, in other words. That’s always the explanation researchers give for the super-hearing of blind people; people who are blind have built up their hearing to compensate for not being able to see.
I’m sure that’s true, but I don’t think it’s the whole story. I think the potential to be able to hear the radio when it’s turned off is already there inside everyone’s brains; we just can’t access it. Somehow a person with sensory problems ﬁgures out how to get to it.
I have two reasons for thinking this. First, there are a lot of cases in the literature of people suddenly developing extreme perception after a head injury. In The Man Who Mistook His Wife for a Hat, Oliver Sacks has a story about a medical student who was taking a lot of recreational drugs (mostly amphetamines). One night he dreamed that he was a dog. When he woke up he found that all of a sudden, literally overnight, he had developed super-heightened perceptions, including a heightened sense of smell. When he went to his clinic, he recognized all twenty of his patients, before he saw them, purely by smell. He said he could smell their emotions, too, which is something people have always suspected dogs can do. He could recognize every single street and shop in New York City by smell, and he felt a strong impulse to sniff and touch things.
His color perception was much more vivid, too. All of a sudden he could see dozens of shades of colors he’d never seen before— dozens of shades of the color brown, for instance.
This happened overnight. It’s not like he lost some other sense and then built up his sense of smell over time to compensate. He dreamed he was a dog and the next morning woke up able to smell things like a dog. The actor Christopher Reeve had a similar experience right after his accident. All of a sudden he had an incredibly heightened sense of smell.
The other important thing to know about this guy is that he hadn’t had any big brain injury that anyone knew about. Dr. Sacks assumes that the heavy drug usage was probably the cause, but there’s no way of knowing. The student continued to function in medical school just ﬁne, and his vision and sense of smell went back to normal about three weeks later. Of course, some part of his brain could have been temporarily incapacitated, but if it was, there’s no obvious way that being able to smell people the way a dog smells people helped him compensate for whatever might have been wrong. The most likely explanation is that he always had an ability to smell like a dog and see ﬁfty different shades of brown, but he just didn’t know it and couldn’t access it. Somehow his heavy amphetamine usage must have opened up the door to that part of his brain.
My other reason for thinking everyone has the potential for extreme perception is the fact that animals have extreme perception, and people have animal brains. People use their animal brains all day long, but the difference is that people aren’t conscious of what’s in them. We’ll talk about this in the last chapter. A lot of what animals see normal people see, too, but normal people don’t know they’re seeing it. Instead, a normal person’s brain uses the detailed raw data of the world to form a generalized concept or schema, and that’s what reaches consciousness. Fifty shades of brown turn into just one uniﬁed color: brown. That’s why normal people see only what they expect to see—because they can’t consciously experience the raw data, only the schema their brains create out of the raw data.
I can’t prove that humans are taking in the same things animals are, but we do have proof that humans are taking in way more sensory data than they realize. That’s one of the major ﬁndings of the inattentional blindness research. It’s not that normal people don’t see the lady dressed in a gorilla suit at all; it’s that their brains screen her out before she reaches consciousness.
We know people see things they don’t know they see because of years of research into areas like implicit cognition and subliminal perception. Dr. Mack and Dr. Rock, who wrote Inattentional Blindness, adapted some of these studies for their inattentional blindness research. They’d do things like ask their subjects to tell them which arm of a cross that ﬂashed onto a computer screen for about 200 milliseconds was longer. Then, on some of the trials, there’d be a word like “grace” or “ﬂake” printed on the screen, too. Most people didn’t notice the word. They were paying attention to the cross, so they didn’t see it.
But Dr. Rock and Dr. Mack showed that many of them had seen the words unconsciously. Later on, when they gave subjects just the ﬁrst three letters of the word—gra or ﬂa—and asked them to ﬁnish them with any word that came to mind, 36 percent answered “grace” or “ﬂake.” Only 4 percent of the control subjects— these were people who hadn’t been subliminally exposed to any words at all—came up with “grace” or “ﬂake.” That’s a huge difference and can only mean that the subjects who were subliminally exposed to “grace” and “ﬂake” really did see “grace“ and “ﬂake.” They just didn’t know it.
So we know that people perceive lots more than they realize consciously. Drs. Rock and Mack say that inattentional blindness works at a high level of mental processing, meaning that your brain does a lot of processing before it allows something into consciousness. In a normal human brain sensory data comes in, your brain ﬁgures out what it is, and only then does it decide whether to tell you about it, depending on how important it is. A lot of processing has already taken place before a normal human becomes conscious of something in the environment. (Drs. Rock and Mack use the phrase high level to mean advanced processing, not necessarily higher levels of the brain. They don’t discuss neuropsychology, just cognitive psychology.)
There are a few things that always do break through to consciousness. I mentioned that people almost always notice their names in the middle of a page of text no matter how hard they’re concentrating on something else; they will also notice a cartoon smiley face. But if you change the face just a tiny bit—turn the smile upside down so it’s a frown, for instance—people don’t see it. This is more evidence for the fact that your brain thoroughly processes sensory data before allowing it to become conscious. With the smiley face your brain has to have processed it to the level of knowing it’s a face and even that it’s a smiling face before it lets the face into conscious perception. Otherwise you’d see the frowny face as often as you saw the smiley face. It’s the same principle with your name. If your name is “Jack,” the word “Jack” will pop out at you in the middle of a page. But the letters “Jick” won’t. That means your brain processes the word “Jack” all the way up to the level of knowing that it’s your name before your brain admits “Jack” into consciousness.
We don’t know why humans have inattentional blindness. Maybe inattentional blindness is the brain’s way of ﬁltering out distractions. If you’re trying to watch a basketball game and a lady gorilla comes into view, your brain screens her out because she’s not supposed to be there, and she’s not relevant to what you’re trying to do, which is watch a game. Your nonconscious brain takes a look at the lady gorilla and decides she’s a distraction.
Being able to ﬁlter out distractions is a good thing; just ask anyone who can’t ﬁlter things out, like a person with attention deﬁcit hyperactivity disorder. It’s hard for humans to function intellectually when every little sensory detail in their environment keeps hijacking their attention. You go into information overload.
But humans probably paid a price for developing the ability to ﬁlter out ladies wearing gorilla suits, which is that normal people can’t not ﬁlter out distractions. A normal brain automatically ﬁlters out irrelevant details, whether you want it to or not. You can’t just tell your brain: be sure and let me know if anything out of the ordinary pops up. It doesn’t work that way.
Autistic people and animals are different: we can’t ﬁlter stuff out. All the zillions and zillions of sensory details in the world come into our conscious awareness, and we get overwhelmed. There’s no way to know exactly how close an autistic person’s sensory perceptions are to an animal’s. There are probably some big differences, if only for the reason that animal perceptions are normal for animals, while autistic people’s perceptions are not normal for people.
But I think many or even most autistic people experience the world a lot the way animals experience the world: as a swirling mass of tiny details. We’re seeing, hearing, and feeling all the things no one else can.