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Brain Brew: How Daily Coffee Habits May Affect Brain Plasticity and Learning - Neuroscience News
(neurosciencenews.com)
Here’s a link to the original study.
This bit from the discussion section echoes my first thought:
it is possible that individuals with innately higher plasticity (for other reasons) are less drawn to caffeine, and that these innate properties are driving the overall difference in the earlier studies as well as our findings here.