John M Keynes may be famous for his metaphors of using “ Beauty Contest “ to explain and describe the investors' perception which caused the price fluctuation in stock market  and “ Musical Chair “ of how investors speculate in the market. You may find these two interesting metaphors here ( Keynes on Beauty Contest ) and here ( Keynes on Musical Chair ) if you have never heard about it. You may also like to read my blog on “ Investing and Storytelling “  ( LINK ) for more detail : There is another important phrase coined by Keynes which might explain the reasons for above two phenomena , which is “ Animal Spirits “.  Keynes believed that although most of the economic activity results from rational economic motivations , but also that much economic activity is governed by animal spirit. Peoples ( investors ) are not always rational in pursuit their economic interest , these animal spirit are the main cause of why economy ( stock market ) fluctuates much as it does ......