Carl Sagan pointed out in his excellent book Broca's Brain that our brains weren't planned, they grew, with each layer being added onto and integrated with the previous one. My own research and experience leads me to believe that this layering reaches into many more places of our consciousness.

For instance, it's one thing to read about short term and long term memory, and how they're discreet and different, but it's a whole other thing to actually experience the separation. I distinctly remember a time in college when friends were staying up late playing cards. I was spending most of my time studying (yes, I did study, if only occasionally), and so decided to "rest my eyes" for a bit. At no point did I consider myself asleep, as I was quite aware of the conversations going on around me, and had an internal dialogue going about what was happening. Suddenly everything stopped and people were yelling at me "Scott, wake up you loser, we gotta go!"

"I am awake, I just had my eyes closed!"

"Nah, you were asleep dude. Totally gone."

"Was not."

"What were we talking about then?"

And then I realized that I couldn't tell them what they were talking about. It was just gone, evaporated like dry ice. I could remember listening, but I couldn't remember what was said.

Ellen thought this was just another weird thing that being married to me came with, up until it happened to her. We were driving to New York one night and, as she tends to do when forced to sit still for any length of time, Ellen fell asleep. I was listening to "All Things Considered", a talk-radio show on NPR. I poked Ellen eventually to wake her up so I wouldn't fall asleep, and received the normal snarl, "I'm not asleep, leave me alone!"

"You were too, you were out cold."

"No I wasn't, I was listening to your stupid NPR thing."

"Really? What was it about?"

"Uh..."

She'd had the same experience. It seems to me that we have different, and at least somewhat independent, mechanisms for perception. As you fall asleep, these mechanisms shut down, but not all at once. In our cases, the mechanism that hooked short term and long term memory together had turned off, but the short term stuff was still running, and the long term stuff just kept writing "listening, listening, listening" into memory without actually inputting anything useful. Sort of like a night watchmen looking at security cameras but not realizing the tape machine had gotten disconnected.

Probably all of us have had the experience as children of trying to very, very carefully and very, very quietly change the TV channel from boring grownup TV to cool cartoons. After all, our parents were quite patently asleep and not watching anything. No matter how quiet, subtle, or careful we were, we'd only have them snort awake and yell "get away from that! Put that back! I was watching that!" They really did think they were at least listening, but we always knew they weren't. Since we were kids we didn't count and back went the boring grownup TV.

Abstract reasoning and elaborate memory structures are a new "layer" to the human psyche, from most indications one that didn't exist until about 35,000 years ago. And, as our history of believing charismatic people instead of smart ones, and survey after survey show, we're still not all that comfortable with it. Our sense of "self" and the sense that the thing sitting next to "self" at the dinner table that just belched impressively is another, different, but co-equal "self" called "wife" doesn't seem to have been around more than 250,000 years or so. Our tendency to turn other people into "things" that can, and even should, be killed shows that we're not completely comfortable with that layer either.

If you spend any time studying chimpanzees, you'll realize that we are still influenced a lot by layers that we're not even all that aware of. I once saw a really impressive chimp colony at the Tulsa Oklahoma zoo. They had a huge enclosure with a gigantic "jungle gym" in the center. There were individuals of all ages, with the young ones ripping around the play set and their elders sitting around the edges grooming each other, eating, or simply watching the juveniles play. I sat and watched them all for hours.

The similarities were more than a little striking when I visited a local mall. From the upper level, I could see on the lower level a huge carpeted area. In the center was a colorful jungle gym, with benches around the edges for adults. The kids were screaming and chasing each other around, while the adults mostly sat and talked with each other, ate, or just tiredly watched the kids go by. From that distance you literally could not see any real difference in the behavior of the two groups.

Nearly everyone has known of a dog or a cat that was terrified of something strange. I've known ones that were afraid of men, very loud noises, and metal rulers (albeit not in the same critter). Nearly always you'll find that the animal was traumatized in some way that could directly associate that trauma with whatever they're now afraid of. In evolution, this is a Good Thing, as it provides a handy way of keeping critters out of trouble without having to build this huge, unreliable cognitive structure. An emphatic, non-verbal association of "FIRE=PAIN=RUN!" is much more efficient at keeping you from getting burned than the internal dialog of "There's a candle burning on the table so I better be careful and not touch it." As with most things that evolution has cooked up, false alarms are considered preferable to screwing it up the one time it mattered.

But before you write this off as just animals being stupid, realize that you know people in your everyday life that act this way. I nearly always flinch when I have to stop quickly on a road because I was rear-ended years ago. Ellen will reflexively yell and grab things when she sees a car stopped and our car is still moving toward it because we got in an accident that way once. I've known people who were afraid of dogs after an attack, people who feared dark places after a mugging, or who become physically ill when smelling smoke after their house had burned down. These are all reflexive, and wrong nearly all of the time, but we do them anyway without even thinking. And therein, I believe, lies a valuable key to understanding the true internal workings of not only the animals around us, but also people who have, through injury or disease, "lost" the upper layers of their, well, onion.

As an experiment, the next time you have one of these reflexive reactions to something, stop for a second. Think about how you felt when that happened, what went through your mind, how you were perceiving things. The next time you see your cat or dog do something like that, realize that they are probably experiencing the same thing inside their head. Imagine living you're whole life in that place and I think you'll come really, really close to what it's actually like being a cat, or a dog, or a deer, or a skunk, or any other mammal at least.

And did you really become any less "you" when you had that reflexive reaction? Did "you" stop just because some other part of your conscious was running the show at that moment?

All of us have been really, really tired and confused at points in our life and simply stopped making sense to the people around us. The next time that happens, try to stop and think about it. Did you stop being "you" at that moment? Did "you" disappear because your cognitive layers had decided to take a breather and let the animal pieces run the show for awhile? I believe that it is during these moments that we come closest to what it feels like to, say, have Alzheimer?s Disease, or Down's Syndrome, or experience a brain injury.

And in a funny sort of way I take comfort in this, because I know that the "you" that is me didn't cease to exist simply because I was acting reflexively, or had gotten cognitively out of synch with the rest of the world. Thinking about these things really brought home to me the true meaning of the Buddhist maxim, "Your perceived self and your real self are like clouds passing over a mirror." Just because the clouds change shape, or get darker, or make it more difficult to see the mirror, doesn't mean the mirror isn't there. And it doesn't mean we can't appreciate the new clouds any less than we could the ones there before. They're always changing anyway.