I think I learn best when I'm utterly fascinated by something. To me it's a state of focused attention (like trance) that carries with it an emotional charge - particular sensations in the body that may not be the same for every learning situation, but usually feel a lot like happiness and anticipation of something positive.
And I agree with Jamie that learning and using (or in the case of tests / exams regurgitating specific content about) what's been learned are best done in the same state. So it would seem that for me I also require a state of happy anticipation and focused attention to usefully apply what I've learned. And to function well (whatever "well" means in a given context) I need to be applying the many things I've learned in the many years I've been learning, so happy, focused anticipation needs to be an easily accessible state. Which it is. I think I anchored it to a smile and a laugh well over sixty years ago

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No wonder - if any of that is true - so many kids hate going to school at various times in their lives. I've mentioned in another thread that I have clear memories of teachers who made me love learning, and nearly no memory of those who didn't. The exception is Mr Rose, who made every schoolday so dismal that I'd sometimes fake being sick to keep from going to school, and my mother would often go along with it just to afford me a break from him. And it wasn't that he picked on me, 'cause he didn't, particularly. He picked on a select, unhappy group of children whom I hope have forgotten his very existence. A teacher that horrible can make a child equate learning with misery, and I know more than a few adults who seem to hold that view.
So as well as optimal learning states, there are a plethora of sub-optimal non-learning states, or perhaps anti-learning states. How I wish teachers learned
this before being turned loose on a classroom full of unsuspecting children.