This article (Spanish-language) in La Nacion describes work whose roots lie in an old project of Sigmund Freud and Carl Jung, among others. Both of those luminaries spent considerable time and effort on the ‘word association problem’: trying to divine when and why certain words were associated with each other in many people’s minds. Mariano Sigman, Martin Elias and Flavia Bonomo of the University of Buenos Aires applied mathematics to the problem, using a huge corpus of text from newspapers and books to develop a metric which determines how “close” and “far” different words typically are from each other. The associations given by their metric appear to do a pretty good job mirroring the responses people give when given a word and asked to say what pops into their head.