Behaviorists suggest that paraphilias develop because some behavior becomes associated with sexual pleasure through conditioning (G. D. Wilson, 1987). For example, imagine that a boy gets an enema. While receiving it, the boy has an erection, either by coincidence or because he finds the stimulus of the enema pleasurable (it becomes a reinforcement). Later, remembering the enema, he becomes excited and masturbates. As he repeats his masturbatory fantasy, a process called conditioning occurs, whereby sexual excitement becomes so associated with the idea of the enema that he has trouble becoming excited in its absence.
You can imagine how similar situations could lead to other types of fetishes: A boy lies naked on a fur coat, or takes a “horse” ride on his aunt’s long black leather boots, or
puts on his sister’s panties, or spies on a female houseguest through the bathroom keyhole. All of these behaviors become positively reinforced and thus are more likely to be repeated.