As judged by motor responses to a variety of stimuli, humans perform most effectively in early adult life. Although this superiority is most evident in tasks of some complexity, in which judgment or response readiness may be important factors, it is also apparent to some degree in relatively simple voluntary responses to less complicated stimuli.1-7 The stage at which peak performance appears is dependent to some degree on the complexity of the task. In any case, the optimum is reached only after a considerable period of maturation, and is succeeded by progressive functional decline throughout the remaining years. The physiological mechanisms involved in these slowed total motor responses of the very young and of the elderly, as compared with adults in their prime, remain obscure.Objective indices of senescence, apart from the results of disease, in receptor end-organs of vision, hearing or somesthesis have been few and equivocal.8
MAGLADERY JW, TEASDALL RD, FRENCH JH, BUSCH ES. Cutaneous Reflex Changes in Development and Aging. AMA Arch Neurol. 1960;3(1):1–9. doi:10.1001/archneur.1960.00450010001001
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