A study of the effect of placebos on three hundred thirty-four medical students showed that thirty-four per cent reacted—twenty per cent favorably and fourteen per cent unfavorably. It was also found that the sensitivity of the same symptom to placebos varies according to the clinical syndrome; thus, a non-migrainous headache is improved in a higher percentage of cases than a migrainous one. General personality characteristics and individual experiences also affect the reaction, as does the manner of administration and the relationship between the