It is not clear how Linda came to associate the anus with sexuality. Her account, as we have seen, had her acting upon a sudden whim and inserting a finger into the anus of the man whom she was fellating. Try as she might, she could not recall ever having given any special thought to the anus before that experience. Psychiatrists are rightly skeptical of the sudden, whimsical action and rightly suspect that startling variations from habitual behavior-such as Linda displayed in inserting her finger into her partner’s rectum-are almost always the result of a long, if unconscious, period of preparation. It is thus probable that she was unconsciously forming an interest in the anus long before that act and that she had in fact come to associate it with sexual response.

This kind of behavior is not unknown to students of human sexuality. Long ago, Havelock Ellis remarked that “it would thus seem probable that in some persons … there is a tendency for the centers of sexual excitation to be shifted posteriorly, such persons possessing unusually developed buttocks and an anus with greater sexual sensibility than the normal sexual centers. Such a state of things must be regarded as constituting a predisposition only; it is not necessarily final or beyond the reach of training. But it is obvious that it constitutes a favorable and even natural basis for various sexual deviations.” (Studies in the Psychology of Sex, vol. II, Part 2, p. 198.) We might also consider the fact of Linda’s relative lack of interest in vaginal intercourse. Even at the time of her interview, she stated a strong preference for the other types of sexual activity mentioned in the foregoing portion of her case history.