We published the Rationality Quotient: Toward a Test of Rational Thinking (Stanovich, West & Toplak, 2016) to provide a prototype measure to assess rational thinking in adults based on the cognitive science literature on reasoning, judgment and decision-making. The prototype measure was called the Comprehensive Assessment of Rational Thinking (CART). This measure is composed of many different subtests and supplementary thinking dispositions. The theory, empirical research and sample items are described in this book. The complete set of subtests and thinking dispositions from the CART are posted on this website. We have also developed the Assessment of Rational Thinking for Youth (ARTY) 13-18 years of age, which is based on the CART. The ARTY is composed of 5 subtests and 2 supplementary thinking dispositions. The publication for the ARTY and complete set of subtests and thinking dispositions are also posted on this website.