The psychological influence of the work dances is still easier to understand. Preliminary movements, even when undirected, always make the subsequent action more effective; witness a golfer’s flourish before driving. As Lagrange has pointed out, their effect will be to develop that amount of animal heat which is necessary for every muscular contraction.[405] When, moreover, they are fixed and differentiated in their form, the influence will of course be all the greater. By every attempt to execute a special movement, the idea of such movement is made more and more distinct. And as hereby the ideomotor force of this representation is increased, the final action must be executed with greater ease and greater efficacy. The validity of this law may be easily proved by experimental psychology. Féré has in his dynamometrical tests observed that the second pressure always attains a higher figure than the first one. “La première pression a pour effet de renforcer la représentation mentale du mouvement.”[406] Without any theoretical knowledge of these psychological facts, the common man has always been able to avail himself of the beneficial effects which are to be derived from preliminary imitations of any difficult movement. Hence the curious pantomimes of experimentation which we may always observe in the artisan who has to give a finishing touch to his work, or in the athlete who tries to perform a new and unaccustomed exercise. The psychology of movement-perception, as we have described it in the foregoing, makes it evident that a similar prompting influence may be exercised by the actions of others.[407] This is an experience which must have occurred, we should imagine, to every one who has been coached in golf by a professional. When concentrating his attention upon each successive movement in the instructor’s model performance, the beginner in sports and gymnastics receives with his whole body, so to speak, an impression of the exercise he has to go through. The representation thus gains in distinctness as well as in motor force, and the subsequent movement is executed in an almost automatic way. These familiar facts from the psychology of everyday life will explain why among the savage tribes we so often meet with the institution of the præsul. When any labour is to be performed which requires the co-operation of many hands, such as the harvest or rowing, the præsul demonstrates in dance or pantomime the sequence of movements which the others have to go through.[408] By the suggestive influence of his performance all the individual workers are stimulated in their exertions. More important, however, than this stimulation is the co-ordination of labour which is effected by the element of rhythm in song and dance.