A Theory of Laziness (1)

I am developing a theory about laziness.

The phenomenon of ego depletion has been observed. It describes the observable limitation of attention and self-control. A famous experiment showed that people are more likely to reach for a chocolate cake over fruit after a mental exercise.

Is mental capacity and its exhaustion analogous as physical strength?

To an extent, yes.

When I am well rested, I can run/swim/skate harder than when I am tired. I am tired when I have done a certain amount of physical activity. This is not so apparent in mental effort, because most mental activities during the day do not bring on a sore brain, just like walking around for a few minutes at a time, doing some very light housework, or driving the car would not cause sore muscle. However, the muscle gets sore quickly and reliably if I lift a couple of dumbbells up to my capacity. I have become aware that certain mental exertions can be similarly exhausting. For example, I was reviewing the statistical analysis plan of a study I just picked up yesterday afternoon. After spending almost two hours with full and deep attention on the document, I could not finish it. My reading and thinking speed slowed down considerably. I knew my brain was tired. I had to rest a bit, go on to some less strenuous work, and resume the mental "heavy lifting" today.

We instinctively prefer sitting to standing, standing to walking, walking to running. Without added reasons --- improving health, building muscle, losing weight --- we naturally choose resting to activity. Resting takes up less energy, obviously. The instinct likely came from the need for energy preservation during the long history of food/energy scarcity. Among all organs in the body, the brain is disproportionally energy expending. So it makes sense that our instinct also favors a state of inaction in the brain. Like physical objects, the body would return to the low-energy state as much as possible. It burns energy to do strenuous activity, mental or physical.

In other words, being lazy is a natural instinct. Without other factors, we would all be lazy if we can.

Of course, things are never so simple with the brain.