In this episode, we discuss the paper "In defense of external invalidity" by Douglas Mook.    Shownotes Mook, D. G. (1983). In defense of external invalidity. American Psychologist, 38(4), 379–387. Mook, D. G. (1989). The myth of external validity. Everyday cognition in adulthood and late life, 25-43. The case of Phineas Gage was written up: Harlow, J. M. (1848). Passage of an iron rod through the head. The Boston Medical and Surgical Journal (1828-1851), 39(20)