In 1769, in Paris, a French philosopher Denis Diderot described how a new, luxurious red dressing gown made him miserable rather than happy. The cause of that unhappiness is still being examined by psychologists and marketing professionals some 250 years later. A film by Brendan Miller. For more videos on BBC REEL, visit: https://www.bbc.com/reel/ #bbcreel #bbc #bbcnews