It may be connected with representations—i.e., have a psychical cause. Spencer admits the theory of incongruity, and defines it more precisely. He distinguishes the ascending incongruity, which goes from the less to the greater, and the descending incongruity between the greater and the less. The latter alone provokes laughter. There must be a sudden transition from one intense state of consciousness to one which is much less intense, while forming a complete contrast to it. Thus, while we are listening to a symphony, a sneeze on the part of one of the spectators may make us laugh. During a reconciliation scene, on the stage, between two lovers, after a long estrangement, a goat begins to bleat, and so introduces a comic element. The heightened attention of the first moment is suddenly transferred to a trifling incident which does not supply it with sufficient matter on which to expend itself; the surplus has to find an outlet, and this produces laughter.
The excess of emotion, when it does not give a shock to the whole frame, and is not the result of a contrast, takes another direction—e.g., the automatic actions of certain barristers or other public speakers, of the embarrassed schoolboy twisting his pen between his fingers, etc.
Hecker, in a special work, propounds another hypothesis.[[226]] He connects everything with a typical fact—tickling, which explains the laughter arising from physical, and that arising from mental causes.
In tickling, there is, first, the effect produced by each cutaneous sensation: excitement of the vaso-motor and the great sympathetic nerves, dilatation of the pupil, brightness of the eyes, constriction of the vessels, as may be verified experimentally in the application of a mustard plaster or a sudden effusion of hot water. There is another necessary condition: intermittence; for tickling, there must be change in the rate or direction of the movements, or interruption.
The expiration corresponds to the moment of contact, the expiration to that of interruption; in the first case the diaphragm is raised, in the second lowered. To sum up, tickling is an intermittent excitation of the skin producing an intermittent excitement of the vaso-motor nerves and the respiration, and an alternation of pleasurable and uncomfortable states. But what is the use of laughter in this occurrence? Its function is protective, it compensates for the diminished pressure of the blood on the brain; the frequent expirations which compress the thorax, and consequently the heart, the larger vessels and the lungs, prevent the blood-vessels from emptying themselves.
As to intellectually-caused laughter, Hecker, who borrows his psychology from the æsthetician Fischer, and seems to fuse together the two theories of contrast and superiority, traces all manifestations of this kind to the comic. Now, in the comic there are two simultaneous states: one, pleasurable, the sense of our own superiority; the other unpleasant, the contradiction in the object. Hence a rapid alternation of pleasure and pain. The comic is an intermittent impression, which acts like tickling; it is a psychical titillation which, like the other, shows itself in laughter, and for the same cause. Such is Hecker’s theory in its main outlines.
In conclusion, laughter manifests itself in circumstances so numerous and heterogeneous—physical sensations, joy, contrast, surprise, oddity, strangeness, baseness, etc.—that the reduction of all these causes to a single one is very problematical. In spite of all the work devoted to so trivial a matter, the question is far from being completely elucidated.
V.
The pathology of the æsthetic sentiment would require a work to itself.[[227]] We must here confine ourselves to some remarks on the most general physiological conditions producing it, and on the natural causes nearly always at work to produce deviation.
Can the faculty of artistic feeling be absolutely wanting? Are there cases of complete insensibility to every artistic manifestation, however humble? I do not think it in any wise rash to affirm this. A priori since the existence of moral blindness and religious indifference is certain, it is improbable that a superfluous emotion should have, in all men without exception, an indelible character. As a matter of fact, it is difficult to supply the proof; the insensibility passes unnoticed, having no injurious consequences to the individual or to society. However, partial cases, at least, may be observed. Total insensibility to music is not rare, and if this is a known fact, it is because it is the most easily verified.[[228]] Many people declare that the reading or hearing of poetry bores and wearies them to an extreme degree, and they cannot understand why poets take so much trouble, when it would be so much easier to express themselves in prose.