Researchers, investigating the link between daily coffee consumption and learning, claim that subjects who consumed one cup of coffee a day for one week (the equivalent of 50 mg per day) exhibited improvements in declarative memory. Furthermore, the study revealed that such improvements were longer-lasting than those witnessed in a control group served decaffeinated coffee (decaffeinated contains negligible amounts of caffeine). After a week of learning a list of facts, the subjects who consumed one cup of coffee were able to recall these facts with significantly more accuracy. While daily coffee consumption may aid in the process of forming a greater number of short-term memories, and increase the likelihood that these memories will be stored in long-term memory, the study glosses over an important fact. Many exhibit sensitivities to caffeine, including headaches (both migraine and non-migraine), sleeplessness, heightened anxiety and any number of factors that, when working either alone or in tandem, may actually lead to a decrease in the observed link between caffeine and learning. Nonetheless, despite the fact that the study represents a random sampling – and thus any number of subjects can exhibit any number of reactions to caffeine – if enough subjects continue to display signs of improvements in learning, then this result would not be inconsistent with the study's findings. Still, until the researchers either release more details of this study, or subsequent studies are conducted, the extent to which those with caffeine sensitivity influenced the observed link between coffee consumption and memory will not be fully known.