Daniel Kahneman tells a story about how he used to stroll and do his thinking and collaboration with Amos Twersky. He adds that if he goes on more brisk walks such thinking and collaboration is not possible.
Myself, I’ve noticed that when I go on a hard hike I go into a kind of trance state. My consciousness is definitely altered on these hikes in which I am pushing myself to keep going up the steep hills.
Kahneman’s first experiment as a young psychology PhD explains what’s going on.
Kahneman gave research subjects a reasonably tough cognitive task and filmed their pupils. The task was the N+3 task. You are shown a flashcard with a four digit number randomly like 3651. You are asked to add 3 to each digit and recite the new number. In this case, it’d be: 6984. If you try it in real life with the same experimental ecology and design, you’ll see that it is a tough cognitive task, but it is doable. You put in your working memory the first 4 digit number and in your working memory you add three to each and then report the new number. Kahneman noticed that while people did this task their pupils dilated and after reporting they discharged their working memory, while waiting for the next flash card, and their pupils reversed the dilation and went back to normal. (Also, if someone gave up and stopped trying to do the math, Kahneman would observe through a live video feed that their pupils returned to normal and would ask “Why’d you give up?” before they announced that they didn’t have the result. They’d say, “How’d you know I gave up”?)
We don’t understand everything about the parts of the brain involved in this kind of cognition. But we can talk about the brain in terms of modules. The attention or focus module is tasked heavily during the N+3 challenge. Somehow a module you might call in other contexts, the “self-control” module is required to perform the N+3 task. It takes self-control to keep your attention or working memory on the ball with the numbers and the addition and reporting the result. If your self-control module is tasked doing something else, you can’t do the N+3 task. Kahneman’s experiments show this. Any other requirement on self-control renders the N+3 task impossible to do.
This takes us back to my story of a hard hike and Kahneman’s story of walking faster than a stroll. On walks faster than a stroll, Kahneman reports having to use his self-control module to keep the faster pace, to keep from reverting to a stroll. And he reports that in those situations he doesn’t have the same ability to think creatively on his own or with Twersky.
On my hikes, I have to exert self-control in order to keep going up the hills without stopping. I bet my pupils are dilated on my hard hikes. Under these conditions in which the self-control module is working hard to keep the body doing something like walking fast or doing a hard hike, other cognitive tasks requiring self-control won’t get the resources they need. So on my hard hikes, I can’t entertain deliberative thoughts. I couldn’t do the N+3 task, Kahneman’s research suggests. And my experience is thoughts come and go but I do not control them in a deliberate way. Thus, I have the sense of being in a trance. Yes, I am thinking. Yes, there is a stream of consciousness. But it is not of my choosing. Images and thoughts come and go, but I don’t harbor deliberative thoughts for very long.
On the other hand, lots of behavior (including apparently cognitive behavior) can take place, according to Kahneman’s observations, without the pupils dilating. He notes that some of his subjects would engage in small talk and gossip between tests, but while their pupils were still being filmed, and their pupils would not dilate. Just chatting and being social does not take a lot of self-control, even though being social and communicative is one of the things human being take great pride in — things which we think separate us from the animals.
What’s the moral of the story for those who want to increase productivity? It depends on what you mean by productivity. Do you mean open ended brainstorming or do you mean deliberative problem solving. Lots of good creative thinking can happen without expending much of the limited energy available to self-control and attention. But if you need to perform more difficult and intensive cognitive tasks, then you had better be careful to conserve your self-control for those tasks. Get in a place with few distractions that self-control would have to work to keep at bay. Don’t physically exert yourself beyond meandering and easy strolls.
Any physical activity that makes your pupils dilate is taking away from your cognitive self-control required for deliberate thinking and problem solving.