Mental Modules

A particularly useful concept in understanding human mentation is the “mental module”. Don’t think of a mental module as a particular hunk of the brain that you could cut out with a knife. Instead, think of it as a collection of bits and pieces spread out all over the brain that together tackle a particular class of problem. Because the concept is theoretical rather than anatomical, there is no definitive list of mental modules; different authors cut the pie into different size slices. This is the set of mental modules that I use in this work.

Visual/Spatial Reasoning
This is the oldest of the human mental modules; it was developed by our primate ancestors to facilitate their arboreal lifestyle. As such, it is more thoroughly frozen into hardware -- we can localize it to the occipital lobe of the brain, in the lower rear. (That’s why you see stars when you are hit on the back of the head.) The visual/spatial reasoning module processes visual inputs, building up a spatial map of the world we see, and figures out spatial relationships for things that we cannot directly see; this is useful for navigating terrain.

Social Reasoning
This is the second oldest of the major mental modules; it was developed by our simian ancestors. It handles the intricate deliberations involved in our relationships with other people. You may not think that there’s much to process (especially if you’re a guy), but in fact there’s a lot going on inside your brain that you take for granted. Here’s an example: “Despite the fact that it was 4:00 in the morning, Howard was feeling jaunty when he got home early from his business trip, but his mood changed dramatically when he saw his best friend’s car parked in the his driveway.” It didn’t take you long to figure out the dramatic import of that sentence, but step back for a second and list all the logical statements that went into your conclusions. In a fraction of a second, you were able to marshal a great many facts about human behavior to draw detailed conclusions about this little vignette. That’s your social reasoning mental module at work. It’s better developed in women than in men, because they devote more of their lives thinking about relationships than men do. Little girls play with dolls, while little boys play with guns.

Natural History Reasoning
This mental module is not so universally recognized, but some authors give it an important place. Certainly it represents a critical asset to a hunter-gatherer group. Something like this is surely present in all animals, but it likely did not grow to great size in our ancestors until the time they developed their hunter-gatherer lifestyle. The natural history mental module is composed to two interlocking components: the ability to retain a large database of environmental information, and the ability to recognize and remember causal relationships. Plenty of animals know a great deal about their environment, but their knowledge is specialized, devoted only to their sources of food and their predators. Humans, being weak, slow, and unarmored, had plenty of predators. And being omnivorous required a detailed knowledge of plant and animal life. Hence, humans needed to learn everything about their environment. We moderns, having directed those skills to other purposes, are astounded at the extent of environmental knowledge demonstrated by the last few hunter-gatherer groups on the planet. We have the same capacity for encyclopedic information storage, but we use it for figuring out how to do our jobs, use modern machinery, and cope with a complex social structure.

The other aspect of natural history reasoning is the ability to put those facts together to draw useful conclusions. When the hunter-gatherer examines tracks closely and announces what species made them, how many of them there were, and how long previously they did so, he is applying that encyclopedic knowledge in a causal manner. The concept at work here is “causality”. Hominids were the first animals to grasp causality in a generalized fashion, and to use it to improve their lives. The mental module that permitted them to do this goes by a number of names, but in its earliest form it was applied to the natural environment and so is sometimes called the natural history mental module.

Linguistic Reasoning
Obviously, this is the most recent of the mental modules, developing in parallel with language. It is an extension of the sequential reasoning facilities that are present in all mammals.

Accurate Throwing
This module is minor, but it does demonstrate an interesting item. Did you know that this is the one physical skill in which humans best all other species? Nobody can throw a rock with the accuracy that we can. Why? Because this is how the first hunter/gatherers killed prey. They couldn’t run down prey, and they didn’t have big sharp teeth or a size advantage. But they could throw rocks at the prey, which might injure it and draw some blood. The animal, of course, immediately fled, but the hunters simply followed it until it stopped. Then they crept up on it again and hit it with another rock, and again it would run away. Here another special hominid talent came into play: endurance. Hominids developed special sweat glands that cool them, so they can engage in long-distance tracking. None of the other animals on the African savannah could keep going for hours; they were specialized for short bursts of speed that carried them away from the predator chasing them. But the hominids just kept on coming, and the prey would tire and overheat. This process continued until the prey was overheated and exhausted from running and loss of blood. It simply couldn’t go on any further; that permitted the hunters to close in and make the kill. Of course, other mental modules came into play as well. The natural history module enabled them to track the prey over long distances; the visual/spatial module helped them navigate as they went.

It turns out that throwing a rock accurately requires extremely precise control of the muscles of the arms and the chest, timing accurate to about a millisecond. When it comes to precise timing, neurons are rather sloppy devices; their temporal precision is only good to about 10 milliseconds or so. It is therefore difficult to build a simple neural circuit that can obtain the accuracy required for the task of throwing rocks at prey. Hominids accommodated by building up a complex grouping of many neurons that, taken together statistically, could in fact control the muscles with the kind of precision necessary. But it takes a lot of neurons to get that much precision, and this grouping of neurons might now be thought of as a mental module.

One other tidbit: as many man can tell you, women can’t throw worth spit. Actually, they can still do better than any other animal, but the average woman is considerably inferior to the average man in throwing. That’s because the hunters were men, and this gender-specific specialization has been partially bred into the species. That is also why men have so much extra upper body strength; those upper body muscles are needed to put some power into the throw. Little boys know this; their cartoons and toys depict male monstrosities with ridiculously wide shoulders and narrow waists.

Other Takes on Mental Modules
This is an old idea parading under different names and with many different slicings of the mental pie. Two early versions were put together by Howard Gardner and Jerry Fodor. Gardner called his version the “Theory of Multiple Intelligences”. He identified seven separate intelligences: linguistic, musical, logical-mathematical, spatial, bodily-kinesthetic, introspective, and social. Gardner was coming at the problem from an educational point of view and his divisions were not empirically derived; he simply cooked up seven slices that looked complete and orthogonal. Fodor’s breakdown was based on sensation: he saw modules for each of the senses. Mentation was lumped into one big module. Neither of these two approaches are applicable to our problem. Two researchers blew the doors open on the concept of mental modules: Leda Cosmides and John Tooby. Their big idea was that any theory of mental modules had to be based on empirical results, not somebody’s navel-inspection, however brilliant it might be. At this point all hell broke loose; everybody jumped into the fray with arguments for and against particular slicings of the pie.

It does not appear that the dust has yet settled; indeed, there remain influential writers who reject the fundamental notions underlying mental modules, such as the idea that the human mind has an architecture that arose in response to selective pressures. Different researchers place different emphasis on each of the various selective pressures faced by hominids. Was language a response to tool-making or to sexual selection? Did language in turn form the basis for other modules, or is it a stand-alone module just like the others? The debates rage on, and amateurs like you and I can only watch from the sidelines.

So how well does my pie-slicing comport with current views? I think I’m on safe ground asserting the existence of mental modules, but there are a variety of different terms in use, and “mental module” may now have become passé. The modules I have identified are rather large; some researchers prefer to break them down into smaller units. For example, while I identify "visual/spatial reasoning" and "natural history reasoning", some researchers prefer "geometric intelligence", "physics intelligence ", and "biology intelligence ".

Obviously, this is a topic that will require continual revision as the debate moves forward. But the basic message for the reader is that the brain is organized into mental modules, most of which are pattern-recognizing in nature, but the language mental module is profoundly sequential in nature.

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