Positive identification

When Tal Ben-Shahar first taught positive psychology at Harvard in 2002, eight people signed up for his class and two dropped out. A year later, word had obviously got out: 380 students signed up; the next time, 855. Now his classes attract 1,400 students a term. Here PM asks him about the rise and rise of this field of study and how it can be applied to the workplace to create happier, more productive employees.

Q. What, in a nutshell, is positive psychology?