The conditions
- A clear goal. Not 'study biology'. 'Answer these twelve questions.' A vague task cannot produce flow because you never know whether you're succeeding.
- Immediate feedback. You must know whether you're getting it right, *now*. Reading a chapter provides no feedback whatsoever, which is one reason it's so easy to drift while doing it.
- Difficulty matched to skill. Too easy and you're bored; too hard and you're anxious. Flow lives in the narrow band between, and that band is where good practice questions sit.
- No interruptions. The phone alone is enough to prevent it.
Now look at typical studying: an open-ended goal, no feedback, material either far too easy or far too hard, and a phone on the desk. It's a machine for preventing flow.
Which activities actually produce it
Notice that practice questions satisfy all four conditions almost perfectly: clear goal, immediate feedback, tunable difficulty, and a defined end. So does problem solving. So does retrieval practice.
And re-reading satisfies none of them. It's not a coincidence that the study activities that produce flow are the same ones that produce learning — both of them require you to be *doing* something with a result.
You cannot force it, only permit it
Chasing flow directly is self-defeating: monitoring whether you're in flow is precisely the self-consciousness that prevents it. Set the conditions, start the work, and stop checking. It arrives or it doesn't — and a good session without it is still a good session.