We ladies all know that the menstrual cycle can cause emotional ups and downs, but did you know that high levels of estrogen can actually improve concentration in some women? "Hormone fluctuations during a woman’s menstrual cycle may affect the brain as much as do substances such as caffeine, methamphetamines or the popular attention drug Ritalin," says Scientific American. Neuroscientists at UC Berkeley asked women with naturally low dopamine levels -- dopamine is known to affect short-term memory -- to take some basic memory tests at different points during their menstrual cycles. Women with naturally low dopamine levels fared better on the memory tests while they were ovulating. Thanks, menstrual cycle!