Although the results of studies on the effects of
caffeine on alertness, vigilance and memory are sometimes
contradictory in terms of whether caffeine
produces beneficial effects or no effects, there is little
indication that intake of caffeine (up to approximately
250 mg in a single dose or over a few days)
affects these processes in a negative manner (Smith
1998). However, a single caffeine dose of 100 mg was
shown to affect short-term memory adversely in one
study (Terry and Phifer 1986).