Human beings tend not only sympathetically to reproduce the instinctive actions of others,[2] but they tend, despite themselves, to experience directly and immediately, often involuntarily, the emotions experienced and outwardly manifested by others. Almost everyone has had his mood heightened to at least kindly joy by the presence in a crowded street car of a young child whose inquiring prattle and light-hearted laughter were subdued by the gray restraints and responsibilities of maturity. One melancholy face can crush the joy of a boisterous and cheerful party;[3] the eagerness and enthusiasm of an orator can, irrespective of the merits of the cause he is defending, provoke eagerness and enthusiasm for the same cause among an audience that does not in the least understand what the orator is talking about. [Footnote 2: "In man infectious laughter or yawning, walking in step, imitating the movements of a ropewalker, while watching him, feeling a shock in one's legs when one sees a man falling, and a hundred other occurrences of this kind are cases of physiological sympathy." Ribot: _Psychology of the Emotions_, p. 232. Reproduction of the actions of others has by a certain school of philosophers and psychologists, notably Tarde, Le Bon, and Baldwin, been ascribed to imitation. But no experimental researches have revealed any such specific instinct to imitate (see Thorndike, p. 73 ff.), and "imitations" of acts can generally be traced to sympathy, or suggestion--which is sympathy on an intellectual plane.] [Footnote 3: Such expressions as "kill joy," "wet blanket," "life of the party" are instances of the popular appreciation of the fact of social contagion.] One brand of cigarettes was recently advertised by the face of a young soldier, roguishly irresponsible, palpably and completely given over to joy. One found one's self transported into something of this same mood before one had a chance to speculate at all as to whether there was any causal relation between the specific quality of tobacco the youngster was smoking, and that contagious, undeniable delight. What is called personal magnetism is perhaps more than anything else the ability to provoke in others sympathetic experiences of pleasant and exhilarating emotions. Sensibility to the emotions of others, though possessed by almost all individuals, varies in degree. The complete absence of it marks a man out as "stolid," "cold," "callous," "brutal." Such a type of personality may be efficient and successful in pursuits requiring nothing besides a direct analysis of facts, uncolored by any irrelevant access of feeling, as in the case of mathematics and mechanics. But the geniuses even in strictly intellectual fields have frequently been men of sensitiveness, delicacy, and responsiveness to the feelings of others. That intellectual analysis, however, does frequently blunt the poignancy of feeling is illustrated in the case of John Stuart Mill, who writes in his _Autobiography_: