Computational psychiatry is an emerging field of research that strives to leverage recent discoveries in the computational basis of high-level cognitive functions in order to understand, diagnose, and treat mental illness. Psychiatry is the only field of medicine where there are currently no laboratory tests, due in part to a lack of understanding what is the biological basis of symptoms. Computational theories of the brain's mechanisms for evaluation and decision may provide a foundation for such an understanding, and tasks measuring their function can offer objective measures. This seminar will discuss recent findings in this field.