In meditation parlance, alertness means you are sensitive to changes in where your attention goes. Inattention means not paying attention to what you should be paying attention too; the desired object of attention. If you are alert, then you know when you are paying attention, and when you aren't.
Maybe that's not helpful. Could you perhaps refine or rephrase your question?
I think caffeine is one of those drugs that robs Peter to pay Paul. Has a useful short term effect, but you pay later.
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