In a recent post, I talked about the observation that people are lazy thinkers. They try to minimize the amount of effort they put into thinking. As an example, think about a person standing at the counter at a drug store trying to decide what kind of gum to buy. In my previous post, I suggested that there is a
cognitive economy. The amount of thinking someone will put in will depend on the costs and benefits related to the amount of thinking that they do.
In general, we assume that the more thinking that we do, the better the choice we will make, because we are taking more information into account. For the moment, we'll assume that is true. That is, the more effort someone puts in to make a choice, the more likely that the thing they pick will be the best thing they could have chosen in that situation.
Some of the costs and benefits in a situation depend on the circumstance. If I am buying a pack of gum for myself, then there are some costs. Some are real money costs. The gum itself costs money, and different kinds of gum differ in price. In addition, there may be costs to a bad choice. If I buy a flavor I don't like, then the gum-chewing experience will be unpleasant. There are also potential benefits. A particularly good piece of gum may have an enjoyable taste and may also feel good in the mouth. Different situations might create different costs and benefits. For example, if I'm trying to impress someone with my selection of gum, then there may be social costs to a bad choice.
In my previous post, I suggested that another cost that is used by the cognitive system is physical. The brain consumes a lot of energy. We can consider the energy being used by the brain while thinking about a particular choice as a cost of that choice. So, one cost that people consider is the amount of energy being used to think. I suggested that people try to minimize that energy while still making an acceptable choice.
My colleague Russ Poldrack at UCLA suggested thinking harder about this assumption. There is some evidence from neuroscience, for example, that the amount of energy being used by the brain is about the same no matter how hard you are thinking.
So, I invested some additional energy into thinking about this issue.
There are a few physical costs that are added into our cost-benefit equation. First, there does seem to be a discernable energy cost to difficult thinking. For example, Matthew Gailliot, fellow PT blogger Roy Baumeister and their colleagues have done research suggesting that working hard to regulate your own behavior actually leads to a measurable decrease in the amount of glucose in your blood. Glucose is a main energy supply for the body. So, there are energy costs to doing hard thinking.
In addition, there are other brain chemicals that are involved in complex thought that may require some conservation. For example, Martin Sarter, William Gehring, and Rouba Kozak talk about the neurotransmitter acetylcholine, which the brain uses to maintain focused attention. This attentional system cannot be active full-blast at all times, and so this chemical may provide another limited resource that the brain uses to determine the costs of thinking.
There are other neurotransmitter chemicals that may also become part of the costs of effortful thinking. For example, Gary Aston-Jones and Jonathan Cohen have talked about the chemical norepinephrine. This chemical seems to be involved in people's interest in focusing on a particular option when making choices as opposed to their desire to explore the world. This chemical may also be part of the mental costs of thinking.
The broad conclusion to draw here is that complex thought has a lot of physiological expenses. There is a lot of physical overhead to thinking. The brain needs a lot of energy to think, and hard thinking can actually lead to measurable decreases in the body's energy supply. In addition, there are a number of crucial brain chemicals that are limited resources that must be conserved for important thinking tasks. So, we often try to think as little as possible, unless there are great benefits to be obtained from that thinking or very serious costs to be incurred by not thinking.
