Women think with their hearts (emotionally), men with their brains (logically) - In general that is.
Whether that's because of sociological or biological/genetic reasons mainly is not yet  entirely known I think.
But since they are at their worst when they have their period-induced mood swings...
one could easily suspect it's biological, right? Swings in their Estrogen-levels simply.
It's annoying, sometimes outright dangerous... but it's also kind of cute.  
