"Why do some countries succeed while others struggle? Why are some firms profitable while rivals fail? Why do some marriages thrive and others end in divorce? These questions seem unrelated, but societies, companies, and marriages have one important thing in common: they involve more than one...

Traditionally economists have based their economic predictions on the assumption that humans are super-rational creatures, using the information we are given efficiently and generally making selfish decisions that work well for us as individuals. Economists also assume that we're doing the very...