The concept of instinct espoused in psychology in the early 20th century and the contemporary concept of psychological adaptation invite comparison. Definitions of both employ the notions of inheritance, selection, functional specificity, and species typicality. This article examines how psychologists before the rise of behaviourism sought to establish instinct as a psychological phenomenon. One of the consequences of doing so was a decoupling of psychological and physiological forms of instinct. This led to a failure of constraint in the usage of (...) the term instinct and the abandonment of the project to establish it as foundational. I argue that the notion of psychological adaptations at the heart of contemporary evolutionary psychology as espoused by John Tooby and Leda Cosmides invites similar difficulties and may come to share a similar fate. (shrink)