People keep on criticism the methodology of the study. It's fair game. Here is a more detailed report about the study: http://advances.sciencemag.org/content/2/8/e1600451 What I like in the methodology: -Real significient price for winners of the games. -Random pairing of player. -the grouping of similar behavior was statistic (5 groups was the optimal solution according to "Davies-Bouldin index". This index might be bullshit, but ....hey... sometime you have to be trusting ) -The grouping seems statistically sound and simple (minimize dispersion in cluster) What I dont like: -sample size coming from a fair (might skew the population toward certain type) -They could have report other statistical ways of grouping people to see it the result were still coherent. And btw it's not a personality test per se. It's a solution to the old problem of rational agent in economy. It might be a more precise separation than risk-adverse and risk-takers. And it only apply in collaborative interaction with perfect information (everyone know the chance, and payoff of their decision before hand.. Which never happen in real life) Still a nice tool to have.