Caffeine might have been proven to help prevent memory loss in people who have neurodegenerative diseases. In an experiment in which lab rats were given caffeine over a long period of time, results showed that these lab rats displayed better memory than those that did not receive this treatment. Although the results from this experiment have not been proven to be the same with humans, the results could still be considered a medical breakthrough. It has to be extremely difficult to have even the slightest form of memory loss. If caffeine, which is widely available, is able to prevent memory loss in humans, many other things could be possible. And, obviously, the people with those neurodegenerative diseases will leave better lives.
http://www.science20.com/catarina_amorim/caffeine_may_prevent_memory_loss_diabetes-89734
Could it be possible that the caffeine given to rats in that study yielded some type of state dependent learning? I wonder if they were given caffeine prior to the testing of their memory, which would skew the experiment. Also i think it could just be a heightened ability to learn, not an increased retention of material.