Let's say you wanted to analyze if the purported brain benefit of flavonoids in chocolate actually did anything. How would you go about it? By teaching snails, of course.
Researchers from the University of Calgary set out to better understand the supposed memory benefits of flavonoids, specifically (−)epicatechin (epi), which is found in chocolate, red wine, and green tea. The snail Lymnaea stagnalis has very well understood memory pattern - if you immerse it in deoxygenated water, it'll naturally extend a breathing tube above water. You can teach the snail not to open its breathing tube, and 30 minutes of doing so generally sticks in the snail brain for around three hours.
When exposed to epi, this same half hour training session invoked a memory that lasted 24 hours rather than just the usual 3. Not only that, but when the scientists tried to undo the memory, it remained uniquely resilient. It's not quite clear the exact mechanism that this uses to improve memories — but it's not based on a sensory association, which some previous researchers suggested.
Interestingly, this research involved some of the same people who proved that meth can help your memories, too. So, if a half-bar of dark chocolate isn't doing it, maybe it's time to give Walter White a call.