This essay examines the reception of Ivan Pavlov’s work on conditioned reflexes in early to mid-twentieth century Britain. Recent work on the political interpretation of biology has shown that the nineteenth-century strategy of “making socialists” was undermined by August Weismann’s attacks on the inheritance of acquired characters. I argue that Pavlov’s research reinvigorated socialist hopes of transforming society and the people in it. I highlight the work of Pavlov’s interpreters, notably the scientific journalist J. G. Crowther, the biologist Lancelot Hogben, and the science writer H. G. Wells, who made Pavlov’s work accessible to a British audience and embraced the socialist implications of his research – especially the idea that people could be persuaded to become socialists through science writing for a nonspecialist audience and through use of a simplified language such as Basic English. They saw, in the followers of National Socialism, how Pavlovian conditioning could create a national movement, and believed that this could be used for their own more democratic form of socialism. In the final part of the essay, I suggest that this broad socio-cultural movement to reshape humanity proved controversial, especially in the post-war period and in light of Soviet use of brainwashing. The likes of Aldous Huxley and F. A. Hayek feared that conditioning could only lead to totalitarianism, while the historian E. P. Thompson put forward a socialist humanism that left room for human agency.