1. Studying Chinese-character flashcards while walking on a treadmill is as pleasant as drinking something when thirsty. Unlike actual thirst and drinking, the pleasure lasts a long time and the desire is under your control (to turn it on, you start walking; to turn it off, you stop).

2. What is the opposite of betrayal? There is no antonym. The opposite is so rare it isn’t even obvious what it is. Betrayal is when your friend becomes your enemy; the opposite is when your enemy becomes your friend. Living in China and not knowing Chinese was not exactly my enemy but it was certainly negative. This treadmill discovery turns it into a positive: Chinese becomes an inexhaustible source of dry knowledge that I can enjoy learning.

3. Learning is the central theme of experimental psychology and perhaps all academic psychology. Psychology professors have done more experiments about learning than anything else. Practically all of those experiments have been about efficiency of learning: The amount of learning (e.g., percent correct) in Condition A is compared with the amount of learning in Condition B, where A and B “cost” about the same. As a result, we know a great deal about what controls efficiency of learning, at least in laboratory tasks. I think many psychologists are surprised and disappointed that this research has had little effect outside academia. I have never heard a good answer to the question of why. If you’d asked me a month ago I would have said it’s because they haven’t discovered large non-obvious effects. That’s true, but says nothing about how to discover them.

My treadmill experience suggests a more helpful answer: Hedonics matter. Learning exactly the same material can be more or less pleasant. When Learning X is pleasant, it is learned easily; when Learning X is unpleasant, it is learned with difficulty or not at all. In the real world, hedonic differences matter more than efficiency differences. If they want to improve real-world learning, psychologists have been measuring the wrong thing. It is a hundred times easier and ten times more “objective” (= “scientific”) to study how much has been learned than to study how pleasant was the experience. But that doesn’t mean it is better to study.

Michel Cabanac, a physiologist, strikes me as someone on the right path. Cabanac has studied how the pleasantness of this or that experience goes up or down to help us properly self-regulate. A simple example is that cold water feels more pleasant when we feel hot than when we feel cold. A common example is that exactly the same food becomes less pleasant during a meal. The food doesn’t change; we change.