As a paraphilia , breast fetishism also known as mastofact , breast partialism , or mazophilia  is a highly atypical sexual interest focused on female breasts see partialism. The breasts play roles in both sexual pleasure and reproduction. Scientists have hypothesized that non- paraphilic sexual attraction to breasts is the result of their function as a secondary sex characteristic. For instance, zoologist and ethologist Desmond Morris theorizes that cleavage is a sexual signal that imitates the image of the cleft between the buttocks , which according to Morris in The Naked Ape is also unique to humans, other primates as a rule having much flatter buttocks. Breast fetishism is claimed to be an example of a contagious thought or meme spreading throughout society, and that breasts are features that have evolved to influence human sexuality rather than serve an exclusive maternal function.