Mind-Set Matters In 2007 a Harvard psychologist set out to test her theory that ‘‘Mind-Set Matters."1 She recruited female maids2 working in different hotels to participate in her study, and informed maids (randomly chosen) that the work they do satisfies the Surgeon General’s recommendations for an active lifestyle (which is true), giving the maids examples on how their work qualifies as good exercise. The other maids were told nothing. After four weeks, the exercise habits of the two groups had not changed, but the informed group had lost an average of lbs () and the uninformed group had lost an average of lbs (). The data are stored in MindsetMatters. Based on this study, does ‘‘Mind-Set Matter"? In other words, for maids, does simply thinking they are exercising more actually cause them to lose more weight?