Much of the joy was social. Almost all of Amos' work was collaborative. He enjoyed working with colleagues and students, and he was supremely good at it. And his joy was infectious. The 12 or 13 years in which most of our work was joint were years of interpersonal and intellectual bliss. Everything was interesting, almost everything was funny, and there was the recurrent joy of seeing an idea take shape. So many times in those years we shared the magical experience of one of us saying something which the other would understand more deeply than the speaker had done. Contrary to the old laws of information theory, it was common for us to find that more information was received than had been sent. I have almost never had that experience with anyone else. If you have not had it, you don't know how marvelous collaboration can be ...That is the concluding paragraph from Danny Kahneman's Nobel prize autobiography. Kahneman, a professor at Princeton's Woodrow Wilson School, was awarded the Nobel for economics in 2002. Much of the work he was recognized for was done with Amos Tversky, who died in 1996. Kahneman's piece is one of the most lovely autobiographical sketches I have ever read. It provides a highly engaging survey of breakthroughs in economics and psychology over the past forty years. So if you are a student in either field, that makes for mandatory reading. But more important, it is a generous and moving account of the nature of friendship, which makes it great reading for everyone.