The psychological sciences were deployed in Second World War Britain on an unprecedented scale in the hopes of managing the mobilised population. This chapter traces three groups of psychologists: Bartlett’s experimental psychologists from Cambridge, psychologists from the National Institute of Industrial Psychology (NIIP), and the Tavistock Clinic’s psychoanalysts. It follows their work from peacetime, in the lab, factory, and clinic, to wartime negotiations over how their work should be conducted. Each group had distinct views on the ideal relationship of scientists to military patrons, from disinterested advisors to consultants to involved collaborators. Psychologists’ diverse views on what was valuable in a person shaped (and was shaped by) their methods, revealing three very different approaches to the creation of a science of selection.