Cognitive Science: An Introduction/Modularity vs. General Purpose Functioning

There are four main ways human minds are divided.

Mind vs. Body

We tend to think of all human mental processing as happening in brains, but there other parts of the body, particularly the bowel, that have their own, separate information processing. Our "gut brain" has over 100 million neurons, and has the function of running the computations required to process food. It's largely autonomous from the brain, and continues to work even if the vagus nerve, which connects the gut brain and the brain brain, gets severed.

Left Brain vs. Right Brain

Mammalian brains, including human brains, have two halves, called "hemispheres": the left and the right. Although the whole brain, basically, is active all the time, we can use imaging and other measurement techniques to determine whether some brain areas are more "active" than others during certain kinds of tasks. "Active" means that there is more activity, meaning more neuron firing, energy consumption, and things like that.

In general, the right side of the brain controls the left side of the body (and the left visual field of each eye), and the left brain controls the right side of the body (and the right visual field of each eye). There is nothing profound about this--it could have easily gone the other way, depending on whether the wires had evolved to be crossed or not.

When one hemisphere is more active or important for a task than the other, we call this a "hemispheric asymmetry" or "brain lateraliztion."

You might have heard of some people being "left-brained" or "right-brained." This isn't a good classification for people, but there are differences in what the two hemispheres specialize in. For example, the left brain tends to be more active for language and verbal tasks, and the right brain for nonverbal and especially spatial tasks. This effect is mildly stronger for men than women. That is, women tend to use their whole brain for more activities, and men tend to use one half or the other more.

Controlled vs. Automatized

There is a lot going on in our minds that we're not aware of. For example, if one is asked what one's mother's maiden name is, one is conscious of the name. But when asked how that memory was retrieved, one doesn't know. All that we know is that the information appeared in consciousness.

Very often creative ideas come to us in this way too. Nobel prize winner John Nash also had schizophrenia (he is the protagonist of the film A Beautiful Mind), and he also believed that he was being contacted by aliens. When asked why, he said “Because the ideas I had about supernatural beings came to me the same way that my mathematical ideas did. So I took them seriously.”

What can be confusing is that processing can be unconscious for two basic reasons. First, it can be automatized. That is, it is learned so well that the mind can do it without having to use conscious resources anymore. Driving a car is difficult at first, but eventually one can do it "without thinking" because it is so automatized. Second, it can be an evolutionarily old, evolved process. Your vision system's ability to distinguish objects from their surrounding background is one such ability. You didn't need to learn to do this, you evolved to do it, just like many other animals.

But for many unconscious processes, it's not clear exactly why they are unconscious. Did your brain evolve to think that way, or are you reactin to a lifetime of learning?

New vs. Old

In this book we will use the dual-process theory of the mind and brain to help make sense of many functions of the human mind. The two processes are the old brain (system 1) and the new brain (system 2.)

The old brain tends to be faster, more instinctive, and uses areas of the brain that are evolutionarily older (near the brain stem).

The new brain is near the front of the head, and is associated with deliberative, conscious, step-by-step, slow, strategic thinking.

Often these two processes are in conflict. Imagine having to take a bitter medicine. Why is it hard? Why do you have to force yourself to do it? The dual-process explanation is that the old and new brains disagree on what to do. The old brain thinks it tastes awful and tries to get you to not take it. Your new brain knows you need it, and tries to inhibit the old brain so that you can take it. Whichever one wins this contest of wills determines your behavior.

Can you do everything by learning through trial and error? On the face of it, no. If you are in a new city, and need to get to a museum, you do not use learning from trial and error, at the level of which turns to make on which street, to know how to get there. For that, you need a fundamentally different kind of thinking. That is what the newer, deliberative part of the mind is good at. Some argue that this is what the prefrontal cortex is for.

We can think of the modular parts of the mind and brain as the automatic settings on a camera. They are good for most cases, but occasionally they need to be overridden for particular instances.

According to conflict-monitoring theory, the Anterior Cingulate Cortex (ACC) is responsible for figuring out when the mind is in disagreement. When a conflict is detected, the DLPFC is activated to resolve it, much like appealing to a higher court of law. The ACC is what decides what to do when there are competing goals--say, from a habitual response to one that favors long-term goals.