A method and system for assessing a latent trait such as a psychiatric disorder in a test subject. The method includes receiving a test subject's responses to test items that are administered to the test subject to elicit the responses from the test subject. An initial first sub-region probability of the test subject lying within a first sub-region of a first latent trait is determined from the test subject's response to the initial first test item. A subsequent first sub-region probability of the test subject lying within the first sub-region of the first latent trait is then determined using the test subject's response to the subsequent first test item to ascertain a conditional response probability, and using the initial first sub-region probability as a prior first sub-region probability. The method and system can be used to more accurately and/or more rapidly assess one or more latent traits in a test subject.