The purpose of this study was to explore various ways to predict and measure extreme response style, or overuse of endpoint categories in rating scales. Data was collected from a total of 913 regular participants and 240 peer participants, who completed an online battery of self-report and peer report questionnaires respectively. In addition to verifying the stability and generality of extreme responding, extreme response style was related to two personality predictors: intolerance of ambiguity and decisiveness. Both main effects and interactive effects with speed of survey completion were uncovered. Extreme response style was measured with several simple proportional methods, which were all shown to tap a latent factor of response extremity, and a latent class method, which did not achieve significant relationships with the personality predictors.