Reference has been made to the view of Alrutz, according to which tickling is a milder degree of itching. It is more convenient and probably more correct to regard itching or pruritus, as it is termed in its pathological forms, as a distinct sensation, for it does not arise under precisely the same conditions as tickling nor is it relieved in the same way. There is interest, however, in pointing out in this connection that, like tickling, itching has a real parallelism to the specialized sexual sensations. Bronson, who has very ably interpreted the sensations of itching (New York Neurological Society, October 7, 1890; Medical News, February 14, 1903, and summarized in the British Medical Journal, March 7, 1903; and elsewhere), regards it as a perversion of the sense of touch, a dysæsthesia due to obstructed nerve-excitation with imperfect conduction of the generated force into correlated nervous energy. The scratching which relieves itching directs the nervous energy into freer channels, sometimes substituting for the pruritus either painful or voluptuous sensations. Such voluptuous sensations may be regarded as a generalized aphrodisiac sense comparable to the specialized sexual orgasm. Bronson refers to the significant fact that itching occurs so frequently in the sexual region, and states that sexual neurasthenia is sometimes the only discoverable cause of genital and anal pruritus. (Cf. discussion on pruritus, British Medical Journal, November 30, 1895.) Gilman, again (American Journal of Psychology, vi, p. 22), considers that scratching, as well as sneezing, is comparable to coitus.
The sexual embrace has an intimate connection with the phenomena of ticklishness which could not fail to be recognized. This connection is, indeed, the basis of Spinoza's famous definition of love,—"Amor est titillatio quædam concomitante idea causæ externæ,"—a statement which seems to be reflected in Chamfort's definition of love as "l'échange de deux fantaisies, et le contact de deux epidermes." The sexual act, says Gowers, is, in fact, a skin reflex.[[14]] "The sexual parts," Hall and Allin state, "have a ticklishness as unique as their function and as keen as their importance." Herrick finds the supreme illustration of the summation and irradiation theory of tickling in the phenomena of erotic excitement, and points out that in harmony with this the skin of the sexual region is, as Dogiel has shown, that portion of the body in which the tactile corpuscles are most thoroughly and elaborately provided with anastomosing fibres. It has been pointed out[[15]] that, when ordinary tactile sensibility is partially abolished,—especially in hemianæsthesia in the insane,—some sexual disturbance is specially apt to be found in association.
In young children, in girls even when they are no longer children, and occasionally in men, tickling may be a source of acute pleasure, which in very early life is not sexual, but later tends to become so under circumstances predisposing to the production of erotic emotion, and especially when the nervous system is keyed up to a high tone favorable for the production of the maximum effect of tickling.
"When young," writes a lady aged 28, "I was extremely fond of being tickled, and I am to some extent still. Between the ages of 10 and 12 it gave me exquisite pleasure, which I now regard as sexual in character. I used to bribe my younger sister to tickle my feet until she was tired."
Stanley Hall and Allin in their investigation of the phenomena of tickling, largely carried out among young women teachers, found that in 60 clearly marked cases ticklishness was more marked at one time than another, "as when they have been 'carrying on,' or are in a happy mood, are nervous or unwell, after a good meal, when being washed, when in perfect health, when with people they like, etc." (Hall and Allin, "Tickling and Laughter," American Journal of Psychology, October, 1897.) It will be observed that most of the conditions mentioned are such as would be favorable to excitations of an emotionally sexual character.
The palms of the hands may be very ticklish during sexual excitement, especially in women, and Moll (Konträre Sexualempfindung, p. 180) remarks that in some men titillation of the skin of the back, of the feet, and even of the forehead evokes erotic feelings.
It may be added that, as might be expected, titillation of the skin often has the same significance in animals as in man. "In some animals," remarks Louis Robinson (art. "Ticklishness," Dictionary of Psychological Medicine), "local titillation of the skin, though in parts remote from the reproductive organs, plainly acts indirectly upon them as a stimulus. Thus, Harvey records that, by stroking the back of a favorite parrot (which he had possessed for years and supposed to be a male), he not only gave the bird gratification,—which was the sole intention of the illustrious physiologist,—but also caused it to reveal its sex by laying an egg."
The sexual significance of tickling is very clearly indicated by the fact that the general ticklishness of the body, which is so marked in children and in young girls, greatly diminishes, as a rule, after sexual relationships have been established. Dr. Gina Lombroso, who investigated the cutaneous reflexes, found that both the abdominal and plantar reflexes, which are well marked in childhood and in young people between the ages of 15 and 18, were much diminished in older persons, and to a greater extent in women than in men, to a greater extent in the abdominal region than on the soles of the feet;[[16]] her results do not directly show the influence of sexual relationship, but they have an indirect bearing which is worth noting.
The difference in ticklishness between the unmarried woman and the married woman corresponds to their difference in degree of modesty. Both modesty and ticklishness may be said to be characters which are no longer needed. From this point of view the general ticklishness of the skin is a kind of body modesty. It is so even apart from any sexual significance of tickling, and Louis Robinson has pointed out that in young apes, puppies, and other like animals the most ticklish regions correspond to the most vulnerable spots in a fight, and that consequently in the mock fights of early life skill in defending these spots is attained.