It has been observed that students react in similar ways to mathematics and science tasks that differ with regard either to their content area and/or to the type of reasoning required, but share some common, external features. Based on these observations, the Intuitive Rules Theory was proposed. In this present study the framework of this theory was employed and the reaction times of two types of responses were measured: those that are regarded as intuitive and those that are viewed as counter-intuitive. The motivation behind this study was to empirically address the immediacy characteristics of intuitive responses in the context of science and mathematics. The focus was on the comparison of area and perimeter of geometrical shapes, in the context of the intuitive rule "more A--more B." The main findings showed that the reaction times of intuitive responses were, indeed, shorter than reaction times of counter-intuitive ones. (Contains 1 table and 4 figures.)