"After 1971 he also took amphetamines, despite the concern of his friends, one of whom (Ron Graham) bet him $500 that he could not stop taking the drug for a month.[17] Erdős won the bet, but complained that during his abstinence, mathematics had been set back by a month: "Before, when I looked at a piece of blank paper my mind was filled with ideas. Now all I see is a blank piece of paper." After he won the bet, he promptly resumed his amphetamine use."
It's important to remember this, quoting from another HN comment [1]:
> Erdős was a heavy user of many other stimulants (like coffee), but only started to use antidepressants and then amphetamines in 1971 when he was 58 after his mother died. He was already established as a first rate mathematician (he should have won the Fields Medal), and using amphetamines to work 19 hours a day was his way of coping with the death of his mother.
"After 1971 he also took amphetamines, despite the concern of his friends, one of whom (Ron Graham) bet him $500 that he could not stop taking the drug for a month.[17] Erdős won the bet, but complained that during his abstinence, mathematics had been set back by a month: "Before, when I looked at a piece of blank paper my mind was filled with ideas. Now all I see is a blank piece of paper." After he won the bet, he promptly resumed his amphetamine use."
http://en.wikipedia.org/wiki/Paul_Erd%C5%91s#Personality