Natural selection can only* work in small steps, and without foresight. So evolutionary progress is constrained to small improvements on what we’ve already got in place. Now, those small steps can accumulate to some pretty wonderful and complicated organs and organisms, such as the human brain, but the evolved design is strongly constrained by its evolutionary history. We wouldn’t expect those organs to be as nifty as they might have been if they’d been designed from scratch for a specific purpose. In Kluge, Gary Marcus details the mental errors we make all the time, and suggests that we are prone to making them because of the peculiar history of the evolution of our brains.
Pet peeve: in the first chapter, Marcus describes natural selection as a “satisficing” process, that doesn’t achieve optimal results, but good enough results. That always rubs me the wrong way–natural selection is a local optimizing process, with the caveat that what it’s optimizing is reproductive fitness, not, well, whatever we think a particular interesting organ is supposed to be doing. For example, we look at a liver, think, “Hey, it’s for filtering out poisons!” But no, a liver is meant to increase reproductive fitness, by a) filtering out toxins while b) not wasting too many resources on keeping blood clean as opposed to other vital functions. And as a local process, it suffers from the same failing of any local optimizing process, such as Newton’s Method: it tends to get stuck at the top of whatever local maximum it reaches first.
Anyway, we don’t expect evolution to achieve the best of all possible solution to a problem, but we can often expect that it’s doing as well as it can. The distinction is important, because any sloppiness or sub-optimality we see in an organism can tell us something about how it got to it’s present form, or about how costly a process would be to improve. And Marcus agrees with me about that, so no complaint there, I just don’t like his word choice.
Throughout the book, Marcus does a fine job cataloging our mental mistakes–reasoning error; faulty, fuzzy memories; our clumsy and illogical languages; our miscalibrated pleasure system that we’re eager to cheat. He refers to plenty of cute psychology experiments that explore the holes in our minds that we usually manage to overlook.
For each of our faults, he presents his imaginings of how our brain would work if it were built by a good engineer. To demonstrate how sub-optimal our brains actually are, he tries to tell us how much better they could be. These are often not very convincing–he proposes that we could have “postal code” memories that keep perfect, computer like track of where every datum is in our memories. But…how would we keep track of which code goes with each datum? Postal codes on postal codes? Sure, computers do it, but not really. All a computer does is run a set of arithmetical instructions that someone programmed into it. Interpretation of a computer’s output has always been done by clumsy human brains. When AI researchers try to build software that has contextual/interpretive abilities, that software always makes plenty of mistakes. And it doesn’t come with the ability to introspect it’s own software guts. Anyway, I will concede that our brains could have been built with a relatively small hard-memory module, for example; but expecting all of our memory to be perfect by working on a “postal code” scheme seems pretty far fetched.
I’ll counter-argue with Gary Marcus that our subconscious brain could be more optimal in some of those ways than he realizes, and that some of the mistakes and limitations of our conscious minds will be shared by the most sophisticated AI running on the best computers. I’ll of course concede, again, that we could have, in principle, been built with an integrated 16-bit calculator to help us with arithmetic, and that evolutionary history kept that from happening.
Similarly with language–he discusses logical languages that we could have evolved to understand. These languages would use words with phonic structures (for example) that give clues to their meanings, i.e. similar sounding words could mean similar things. A logical language would also result in a clear, distinct meaning for each statement it’s allowed to make. But–imagine a language that has no ambiguities. How would you (or evolution) know it has no ambiguities? If you only have a few simple concepts to express, such as a language that describes just arithmetic, it can’t be done. Gödel’s theorem. Simple arithmetic contains statements that can’t be proven true. I don’t know what they are. I’m not sure you can know that a particular statement can’t be proven. Now, in English and other human languages, there are plenty of obvious ambiguities, and we could probably do better if we put our minds to it. But how much effort would it take, and would it make evolutionary sense to invest it? Maybe evolution has built our language systems exactly as well as it needed to.
Another thing about language to illustrate the point–we are good at inferring meaning from partial information. At least, better than a computer is when it misses a little bit of information, which can result in a fatal program error. It may well be that the same system that allows us to infer meaning from partial information means we can’t tell so well when we’re saying exactly what we mean to say.
My other main gripe about the book is that Marcus never really discusses what these mental limitations tell us about our evolutionary history. It says right inside the front flap: “How the accidents of evolution created our quirky, imperfect minds.” But if we’re lucky, he’ll tell us that he can easily imagine that there’s a just-so story explaining the mental fault. Without even telling us his story! Great! I’d much prefer examples from other creatures minds, and what they tell us about how our minds work, or don’t work, as the case may be. Not a just-so story, and definitely not a hint that just-so stories are easy to imagine.
The penultimate chapter of the book is almost the most interesting. He discusses mental disorders, and suggests that the particular mental disorders that people suffer can tell us about how our brains are assembled. Great stuff, except that after he makes a persuasive and satisfying argument that it’s possible, he fails to do it. He offers some interesting guesses about what some common disorders might tell us about our brains, though.
Overall, I thought the book was somewhat interesting, and pretty fun and quick to read, but I already knew most of this information from other places that discussed them in more detail, with better context. And since it failed to live up to it’s purported unique, evolutionary history perspective, I was mostly disappointed:/
* “only” in practice; in principle evolution can take very large steps, it’s just that large steps are vastly more likely to break things more than they improve things, while I’ve heard that infinitesimally small steps are about as likely to improve things as they are to break things, so that half of those will be worth keeping, if they can bubble up above the noise
