Do you remember what you had for breakfast yesterday? Chances are, even if you do, it took some mental gymnastics to arrive at your answer.

Why does the mind have trouble with simple tasks like memory recall that any computer could do in a split second with zero errors? Because the brain is the product of evolution, and evolution generally only works with the parts it has, explains Gary Marcus, PhD, a psychology professor at New York University and director of the university's Child Language Center. Marcus's book "Kluge" (Mariner Books, 2009) explores the space between the ideal, optimal mind and what we've got instead. "Kluge" is a term borrowed from engineering meaning a clumsy or inelegant solution to a problem.

Why can't evolution provide us with perfect adaptations?

Evolution sometimes produces really good solutions and sometimes it doesn't. Take the single-column human spine, a kind of minor variation on the kind of spine four-legged creatures have. For them it's very efficient because they distribute their weight horizontally, but we have to distribute the weight vertically and [our single-column spine] isn't a good solution for that. Starting from scratch, with say three columns (in a tripod configuration) would have worked better, but evolution has no foresight and often builds new solutions on top of old ones, however awkward that might be. In "Kluge," I ask whether that same kind of issue arises in the structure of the mind, whether there are analogies to the human spine in the cognitive system.

So just why can't I remember what I had for breakfast yesterday?

One of the central claims in "Kluge" is that we have inherited through evolution a kind of memory structure that works by giving us general tendencies rather than specific information. It works very differently from computers. With a computer, you can just say, "Give me this particular person's phone number," and it's very precise. When we consult our memory, we want something that matches a set of cues. We may get mismatches, we may get a bunch of interference. So our memories get distorted. You may say, "I want to know what I had for breakfast yesterday," and you get confusion because you remember a bunch of different breakfasts on earlier occasions. Or you try to remember where your car is parked but you remember a bunch of different places where you've parked it that blur together. Evolution never stumbled on the simple and elegant system of location-addressed memory that all computers use.

Clearly we're willing to admit that we make mental slipups. Why don't we make the connection to having a faulty mind?

I'm not sure we always even bother to explain that to ourselves. There's a strong literature of psychological errors that I draw on. People are aware of that literature but don't always try to reconcile those errors with other strands of thought. There's a lot of evolutionary psychology that talks about the brain being some kind of optimal tradeoff between different demands that our ancestors faced, for example, but that doesn't necessarily square with the literature on cognitive errors. Part of the point of "Kluge" was to bring these two lines of thought into better contact and try to resolve the relation between one kind of literature that says, "Hey, there are problems with the brain," and other literature that emphasizes ways in which things are pretty well-tuned.

In your book, you mention that evolutionary psychologists often try to explain away imperfections as having some other selective benefit. Why do you think that's problematic?

What evolutionary psychology does well is ask why things are the way they are. I also think that evolutionary psychologists are right to think about what role did this or that aspect of the human mind play historically. What I think is missing is what you might call evolutionary inertia: When we see something in evolution, that's really the product of two things. One is whatever pressures there are, costs and benefits and tradeoffs and so forth. But the other is history, how this thing relates to the set of things that were there before. Evolution doesn't have forethought, it just builds things by accident on top of what came before—once in motion, evolution tends to stay in motion. What's missing in a lot of evolutionary psychology is an attention to what's come before and how that influences what comes next. I agree we need to think about what people in the savannah were doing, we need to think about evolutionary history, but we also need to think about what were the biological mechanisms already in place and how did those change.

Does the 'kluge'-y nature of our brains help explain why we've fallen on economic hard times?

I think we're almost innately born to fall into pyramid scams. We are subject, for example, to the bias of motivated reasoning, where we often allow ourselves to believe what we want to believe. So we see this way to get rich quick, and if we like what we think are going to be the results, we may not be very skeptical. There are ways in which our emotions enter into our decision-making process that make us vulnerable to somebody like Bernie Madoff. The same thing happens with the real-estate market going up and up and up. There's this sort of will to believe. There were people saying that housing is overvalued, but people kept wanting to believe this was the way to get rich. Because of things like motivated reasoning, we tend to believe things that make us feel like we're going to do well, and to only be skeptical when we don't want to believe something.

As someone who researches language development, what can 'kluges' tell us about our imperfect grasp on language?

I think the limits on our memory—the lack of computer-style location-addressable memory—can actually help to answer some otherwise mysterious quirks of language. Why, for example, are human languages ambiguous? Computer languages aren't, and mathematical language isn't, but if I tell you, "The spy shot the cop with the revolver," you don't know whether the spy had the revolver, or the cop did (maybe the other cop had a nightstick). Those sorts of ambiguities could easily be avoided with parentheses; (4 * 3) + 2 is not the same as 4 * (3 + 2), but somehow language never developed parentheses. We use emphasis and we point as a way of getting around ambiguity, but we're only so-so at getting our meaning across. My best guess? We never evolved the linguistic equivalent of memory because our memories would be too feeble to keep track of parentheses even if we had them; the parentheses would blur together, just like your memories of where you parked car. So we make do without.

Now, that doesn't mean we can't have fun with what we've got: Music, poetry, wordplay and so forth may exist only because of quirks in how our brain is wired. But one has to distinguish between what gives us pleasure and why it's there in the first place.