title_body: Effect of Sugar on Perceived Bitterness in Coffee
upvoted_answer: If you are asking whether the science can be trusted, I would say yes.  The effect is already well known.  You even understand it insomuch as you apparently don't drink more concentrated brews (espresso, aerpresso) without a "masking" agent. 
  
  All this study is doing is finding a more specific reason for the already acknowledged effect.  People commonly believe that sugar or salt "masks" the bitterness from caffeine.  This study is saying that sugar or salt are not just masking the bitterness, but actually changing the chemical properties of the caffeine in solution, thus changing the flavor.