Mihaly Czikszentmihalyi: optimum flow occurs when: alienation gives way to involvement, enjoyment replaces boredom, helplessness turns into a feeling of control, and psychic energy works to reinforce the sense of self, instead of being lost in the service of external goals. (Czikszentmihalyi, 1990, p.69)
Czikszentmihalyi, M. (1990). Flow: The Psychology of Optimal Experience. New York: Harper and Row.
It's so complicated now that we know that we have endocrine and hormonal responses to outside events, and those chemicals might make it more or less likely that we'll learn. For example, what do we learn best under stress? Survival stuff?
My son just went through a lot of Army training (he's just been commissioned), and the theory seemed to be that they had to train these young people to accept and use stress. Agreed, many American youngsters are not really trained in that as there's so much intervention involved in keeping them from being stressed (at least in my household-- I am something of a helicopter-style parent, I will admit). But the Army, which does train great numbers of young people, obviously thinks that stress is a good promoter of certain learnings.
I bet you can learn "instinct stuff" (like shooting back, or turning into a skid when you drive on ice) better under stress. But I can't imagine learning anything I have to THINK about under stress.
Are there hormonal/chemical changes that make it easier or harder to learn? I suppose that's the chemistry behind Ritalin and Adderall and those ADD drugs.
I just know I've never been any good at learning on deadline. I'm pretty good though at producing on deadline-- writing a paper that's due tomorrow, I mean. I don't do that anymore because I don't like the anxiety, but I can write fast when I need to.
But I don't know if that is "learning." I can't retain any information when I read fast, for example.