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A ratchet effect is an instance of the restrained ability of human processes to be reversed once a specific thing has happened, analogous with the mechanical ratchet that holds the spring tight as a clock is wound up. It is related to the phenomena of featuritis and scope creep in the manufacture of various consumer goods, and of mission creep in military planning. Ratchet effect in sociology: "Ratchet effects refer to the tendency for central controllers to base next year's targets on last year's performance, meaning that managers who expect still to be in place in the next target period have a perverse incentive not to exceed targets even if they could easily do". (Bevan and Hood 2006, p. 521) ==Examples== ;Famine cycle Garrett Hardin, a biologist and environmentalist, used the phrase to describe how food aid keeps people alive who would otherwise die in a famine. They live and multiply in better times, making another bigger crisis inevitable, since the supply of food has not been increased.〔Malthus, T. (1798). An Essay on the Principle of Population. London: Printed for J. Johnson, in St. Paul's Church-Yard.〕 ;Governance Austrian School economist Robert Higgs used the term to describe the seemingly irreversible expansion of government in times of crisis in his book ''Crisis and Leviathan''.〔Robert Higgs (Crisis and Leviathan ), OUP, 1987, ISBN 0-19-505900-X〕 Similarly, governments have difficulty in rolling back huge bureaucratic organizations created initially for temporary needs, e.g., at times of war, natural or economic crisis. The effect may likewise afflict large business corporations with myriad layers of bureaucracy which resist reform or dismantling. ;Production strategy The ratchet effect can denote an economic strategy arising in an environment where incentive depends on both current and past production, such as in a competitive industry employing piece rates. The producers observe that since incentive is readjusted based on their production, any increase in production confers only a temporary increase in incentive while requiring a permanently greater expenditure of work. They therefore decide not to reveal hidden production capacity unless forced to do so. ;Game theory The ratchet effect is central to the mathematical Parrondo's paradox. ;Cultural anthropology In 1999 comparative psychologist Michael Tomasello used the ratchet effect metaphor to shed light on the evolution of culture.〔Tomasello, M. 1999. ''The Cultural Origins of Human Cognition''. Cambridge, MA: Harvard University Press.〕 He explains that the sharedness of human culture means that it is cumulative in character. Once a certain invention has been made, it can jump from one mind to another (by means of imitation) and thus a whole population can acquire a new trait (and so the ratchet has gone "up" one tooth). Evolutionary psychologist Claudio Tennie, Tomasello, and Josep Call call this the "cultural ratchet" and they describe it in both human and chimpanzee culture.〔Tennie, C., Call, J. and Tomasello, M. 2009. Ratcheting up the ratchet: on the evolution of cumulative culture, ''Phil. Trans. R. Soc. B'' 2009 364(2405-2415). http://www.eva.mpg.de/psycho/pdf/Publications_2009_PDF/Tennie_Call_Tomasello_2009.pdf〕 ;Developmental Biology Receptors which initiate cell fate transduction cascades, in early embryo development, exhibit a ratchet effect in response to morphogen concentrations. The low receptor occupancy permits increases in receptor occupancy which alter the cell fate, but the high receptor affinity does not allow ligand dissociation leading to a cell fate of a lower concentration. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「ratchet effect」の詳細全文を読む スポンサード リンク
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