Durante gli studi di medicina, Ferrier cominciò a collaborare come assistente del noto psicologo e filosofo Alexander Bain (1818-1903), libero pensatore nonché fondatore della psicologia associazionista. ###>As a medical student, he began to work as a scientific assistant to the influential free-thinking philosopher and psychologist Alexander Bain (1818–1903), one of the founders of associative psychology.