The experiments are not completely consistent with one another but they justify general conclsion that caffeine is a stimulant mild doses it usually produces some Shin We on such measures of effciency as tapping typewriting adding end suhsmc ng and simple problem solvmg Sometimes however large doses of caffeine may My irnpair performance but the genei al effect of the drug mild doses is to help rather 1 that to im alr ef ciency It should be added however that caffeine is habit forming and l m habit is acquired people may Show drowsmess headaches dizziness and other discomforts-factors that impair efficiency-whan they are deprived of their regular ration of caffeine