Sexual science or sexology arose in the last three decades of the nineteenth century, when psychiatrists and neurologists began to study and treat deviant sexualities as sickly 'perversions'. The new science of experimental psychology did not engage with this morally contested subject. Research into sexuality was rooted in a biomedical and clinical approach. All the same, in the late nineteenth and early twentieth century, some medical experts increasingly explained perversion as well as regular sexuality in a psychological way. This trend was intertwined with the changing definition of sexuality as either a pushing or a pulling force, which pertained not only to biological versus psychological interpretations, but also to the contrast betw...