French experimental psychology, a newly institutionalized field in 1889, is fundamental for understanding the artistic avant-garde's engagement with alterity-altered states of being as well as individuals considered to be "other"-in the late nineteenth and early twentieth centuries. A foundational tenet of the newly rationalized psychology held that the human mind and human activities such as creation were best understood through the study of pathological states (hypnosis, somnambulism and automatism) as well as ''pathological" people (the mentally ill, children and ''primitives"). Numerous articles in avant-garde publications such as La Revue blanche and the Mercure de France reviewed and discussed the latest developments in the burgeoning field that seductively believed all aspects of the human mind to be understandable and best investigated through the application of the pathological method. This dissertation analyzes how the theories of experimental psychology were filtered and transformed through artistic communities of interpretation grouped around these two publications, from the Nabis and the Strindberg circle in the 1890s to that of Apollinaire prior to 1914. A studied consideration of experimental psychology's incursion into artistic circles, before Freud's eclipsing of the French tradition, will provide an entirely new understanding of this avant-garde's voracious, reinvigorated search for pure aesthetic experience outside the narrow boundaries of Western cultural norms.