The title of Gary Marcus’s bit of popular neuropsychology comes from the computer world, in which a “kluge” (rhymes with “huge”) is “a clumsy or inelegant solution to a problem.” Marcus’s thesis is that the human mind is a kluge, emphasized in his subtitle: “The Haphazard Construction of the Human Mind.”
He argues that our core thinking processes — from memory to belief, from language to our pursuit of pleasure — aren’t purpose-built. Rather, they are add-ons and repurposings of more primitive brain activity. The human mind is thoroughly a product of, and profoundly constrained by, its evolutionary origins.
Marcus makes his case clearly, but Kluge is not a particularly scholarly book. Its 176 pages rush through important concepts and seminal experimental results with carefree ease. This makes it quite readable, but at its core Kluge is an entry-level book.
It’s true that neuropsychology has advanced considerably in the five short years since the book’s publication, but most if its perceived lightness is intentional. Kluge is unashamedly basic, written for the interested newcomer. Kluge does not stand comparison to more involved and detailed general readership books like Antonio Damasio’s Self Comes to Mind. Marcus’s book is more like David Eagleman’s Incognito. The caution is more a bit of information than a criticism. Kluge has no pretensions to deep scholarship, but if you’re looking for an easy, general introduction to the subject, it’s a good choice.
Marcus stresses that we humans came equipped with the basic mammalian brain, creating the “ancestral” or “reflexive” mind upon which later adaptations built the “deliberative” or “rational” mind of which we most often think when we distinguish “mind” from brain. It’s not that “mind” is something other than brain. Rather, “mind” is the configuration of the brain that has resulted from human adaptation to its early (and, to some extent, current) environments.
The reflexive system is clearly older, found in some form in virtually every multicellular organism. It underlies many of our everyday actions, such as the automatic adjustment of our gait as we walk up and down an uneven surface, or our rapid recognition of an old friend. The deliberative system, which consciously considers the logic of our goals and choices, is a lot newer, found in only a handful of species, perhaps only humans.
The last five years of research have made Marcus’s last speculation less likely, but his general claim is strongly supported.
As a result, our minds have many glitches and gaps, many flaws and failings. Everyone is familiar with the best known limitations and distortions to which our minds are susceptible. Are these two lines, with arrows pointing in on one and out on the other, the same length? Why can’t we remember more than seven new things for more than a minute or two? Is the cube in this drawing sinking in, or is it sticking out? And many more.
The answer isn’t that our minds are badly designed. The answer is that they aren’t designed at all. Like the vestigial leg bones that are found in whale skeletons, and the remnants of gills that help us keep our balance, the higher processes of our minds are new uses for old systems. They don’t work perfectly because they weren’t engineered — they were chosen as the best available ways to do advantageous things.
Later in the book, Marcus speculates that our deliberative minds may not be a product of evolution at all. That is, we may have an evolved reactive mind and a learned ability to reason deliberately. In his chapter on belief, Marcus points out how often our “two minds” are in conflict, previous belief (to which the reactive mind has an emotional attachment) competing for supremacy with our inferential ability.
Marcus points out that “people evaluate syllogisms using two different neural circuits, one more closely associated with logic and spatial reasoning (bilateral parietal), the other more closely associated with prior belief (frontal-temporal).” He speculates:
In fact, truly explicit reasoning via logic probably isn’t something that evolved, per se, at all. When humans do manage to be rational, in a formal logical sense, it’s not because we are built that way, but because we are clever enough to learn the rules of logic (and to recognize their validity, once explained). While all normal human beings acquire language, the ability to use formal logic to acquire and reason about beliefs may be more of a cultural product than an evolutionary one, something made possible by evolution but not guaranteed by it.
Later, writing about choice, Marcus emphasizes that “what makes the human mind a kluge is not the fact that we have two systems per se but the way in which the two systems interact.” What we have, he says, “falls between two systems — an ancestral, reflexive system that is only partly responsive to the overall goals of the organism, and a deliberative system (built from inappropriate old parts, such as contextual memory) that can act in genuinely independent fashion only with great difficulty.”
While it’s true that Kluge is not primarily scholarly, Marcus’s book is nevertheless often insightful and engaging in its conversational way. There’s a reason that both Steven Pinker and Jonathan Haidt were willing to write highly-positive praises for the book’s back cover blurbs.
I prefer books with a bit more detail, and with a bit more thorough exploration of opposing viewpoints; still, ll in all I found Kluge to be worth the short time it takes to read. There are enough bad neuropsychology books out there (starting with anything by Malcolm Gladwell) to put Marcus’s effort squarely in the plus column.