I’ve got another lukewarm recommendation for you!  I just finished Steven Pinker’s How the Mind Works. Pinker, like Daniel Dennett, doesn’t lack for ambition. He really wants to tell you how to design a functioning mind, or to be precise, how evolution has put ours together.


His focus throughout is on evolution, so a basic restraint is that the components of the mind should have increased reproductive success. Not absolutely– we obviously use our brains in many ways that couldn’t be adaptations.  But it’s a good restraint to have, as it keeps him from accepting simplistic ideas that “intelligence is good” or that evolution is aiming at creating humanoids. (There’s a major caveat here, though: adaptation is only one process in evolution, and you have to make a case that it produced any particular feature. More on this later.)

Does he succeed?  In parts, brilliantly.  The chapter on vision is excellent. He explains exactly why vision is such a hard problem, and how the eyes and brain could put together a view of the world. Cognitive research is frustratingly indirect– we can’t really see how the software runs, so to speak. But we can put a whole bunch of clues together: how the eye works, what goes wrong when the brain is damaged, what constraints are suggested by optical illusions and glitches, how people respond to cleverly designed experiments.

As just one example, it seems that people can rotate visual images, as if they have a cheap, slow 3-D modeling program in their heads– and that this rotation takes time; certain tasks (like identifying whether two pictures depict the same object) take longer depending on the amount of rotation required. But even stranger, it’s found that people don’t just store one view of an object.  They can store several views, and solve rotation problems by rotating the nearest view. This is fascinating precisely because it’s not a solution that most programmers would think of. It makes sense for brains, which basically allow huge data stores but limited computational power.

He points out that vision is not only a difficult problem, it’s impossible.  If you see two lines at a diagonal in front of you, there is no way to determine for sure whether they’re really part of a triangle, or parallel lines moving away from you, or a random juxtaposition of two unrelated lines, and so on. The brain solves the impossible problem by making assumptions about the world– e.g. observed patches that move together belong to the same object; surfaces tend to have a uniform color; sudden transitions are probably object boundaries, and so on. It works pretty well out in nature, which is not trying to mislead us, but it’s easy to fool.  (E.g., it sure looks like there’s a hand holding a brain-patterned Rubik’s cube up there, doesn’t it? Surprise, it’s a flat computer screen!)

I also like his chapters on folk logic and emotions, largely because he defends both.  It’s easy to show that people aren’t good at book logic, but that’s in part because logicians insist on arguing in a way that’s far removed from primate life. A classic example involves the following query:

Linda is 31 years old, single, outspoken, and very bright. She majored in philosophy. As a student, she was deeply concerned with issues of discrimination and social justice, and also participated in anti-nuclear demonstrations. What is the probability that Linda is a bank-teller? What is the probability that Linda is a bank-teller and is active in the feminist movement?

People often estimate that it’s more likely that Linda is a feminist bank teller, than that she’s simply a bank teller. This is wrong, by traditional logic: A ∧ B cannot be more probable than B. But all that really tells us is that our minds resist the nature of Boolean logic, which considers only the form of arguments, not their content. We love content. People’s judgments make narrative sense.  From the description of Linda, it’s clear that she’s a feminist, so a description that incorporates her feminism is more satisfying. In normal life it’s anomalous to include a bunch of information that’s irrelevant to your question.

As for emotions, it’s widely assumed that they’re atavistic, unnecessary, and positively dangerous– an AI is supposed to be emotionless, like Data. Pinker makes a good design case for emotions. In  brief, a cognitive being needs something to make it care about doing A rather than B… or doing anything at all. All the better if that something helps it avoid dangers, reproduce itself, form alliances, and detect cheaters.

So, why do I have mixed feelings about the book? A minor problem is breeziness— for instance, Pinker addresses George Lakoff’s category theory in one paragraph, and pretty spectacularly misses Lakoff’s argument. He talks about categories being “idealized”, as if Lakoff had overlooked this little point, rather than discussing it extensively. And he argues that the concept of “mother” is well defined in biology, which completely misses the distinction between ordinary language and technical terms. He similarly takes sides in the debate between Napoleon Chagnon and Marvin Harris, with a mere assertion that Chagnon is right. He rarely pauses to acknowledge that any of his examples are controversial or could be interpreted a different way.

More seriously, he doesn’t give a principled way to tell evolutionary from cultural explanations. This becomes a big problem in his chapter on sex, where he goes all in on evolutionary psychology. EP is fascinating stuff, no doubt about it, and I think a lot of it is true about animals in general. But which parts apply to humans is a much more contentious question.  (For a primer on problems with EP, see Amanda Schaffer’s article here, or P.Z. Myer’s takedown, or his direct attack on Pinker, or Kate Clancy’s methodological critique.) Our nearest ancestors are all over the map, sexually: gorillas have harems, chimpanzees have male dominance hierarchies with huge inter-chimp competition for mates (and multiple strategies); bonobos are notorious for female dominance and casual sex.  With such a menu of models, it’s all to easy to project sexist fantasies into the past. Plus, we know far less about our ancestors than we’d like, they lived in incredibly diverse environments, and evolution didn’t stop in 10,000 BC.

Plus there’s immense variety in human societies, which Pinker tends to paper over.  He often mentions a few favorite low-tech societies, but all too often he generalizes from 20C Americans.  E.g. he mentions perky breasts as a signal of female beauty… um, has he ever looked at an Asian girl, or a flapper, or a medieval painting?  Relatedly, Pinker convinces himself that men should be most attracted to a girl who is post-puberty but has never been pregnant, because she’s able to bear more children than an older woman. Kate Clancy’s takedown of hebephilia is relevant here: she points out that girls who bear children too early are likely to have less children overall, and that male chimps actually prefer females who have borne a child.

Finally, the last chapter, on art and religion, is just terrible. He actually begins the discussion of art with an attack on the supposed elitism of modern art. It’s like he’s totally forgotten that he’s supposed to be writing about evolution; what the hell does the supposed gulf between “Andrew Lloyd Webber [and] Mozart”, two Western artists separated by an evolutionary eyeblink, have to do with art in general? Couldn’t he at least have told us some anecdotes about Yanomamo art?

As for religion, he describes it as a “desperate measure… inventing ghosts and bribing them for good weather”. Srsly? Ironically, earlier in the book, he emphasizes several times that the facts about the ancestral environment are not normative, that we can criticize them ethically.  Then when it comes to religion he forgets that there’s such a thing as ethics; he just wants to make fun of the savages for their “inventions”. (I could go on all day about this blindness, but as just one point, the vast majority of believers, in any religion, invent nothing.  They accept what they’re told about the world, a strategy that is not exactly foreign to Pinker– why else does he supply a bibliography?)

On the whole, it’s probably a warning to be careful when you’re attempting a synthesis that wanders far outside your field. It might be best to skip the last two chapters, or just be resigned to a lot of eye-rolling.