what is jekyll and hyde 
the phrase jekyll and hyde employs a literary reference to describe a stock market that appears to have a split personality mixing good and bad character traits jekyll represents the good in a market it is benign predictable and conducive to trading gains hyde is a bad character who is volatile unstable unpredictable and generally dangerous to investors because the stock market is susceptible to the full range of human emotions jekyll and hyde make frequent appearances on wall street understanding jekyll and hydein robert louis stevenson s the strange case of dr jekyll and mr hyde dr jekyll a decent and congenial scientist unleashes his dark side mr hyde through unwise experimentation on himself in a laboratory although jekyll and hyde have contradictory natures they are one and the same person the embodiment of good and evil in one man is at times paralleled in the stock market a calm and predictable market can suddenly and inexplicably be torn apart by a frenzy of negativity like the characters in stevenson s novel market participants and observers are left baffled about this strange behavior and at a loss to explain its underlying causes an economist would say that strange market behavior is at odds with the efficient market hypothesis which maintains that the price of any stock at any given time will always be the same as its fair market value because it will be based on all of the information then available a relatively new field of theory behavioral finance attempts to explain how rational decision making or a lack of it contributes to manic swings in a market collective human behavior connected to greed and fear causes bubbles to form and then suddenly pop the jekyll and hyde syndrome might illustrate an aspect of behavioral finance 