Com~jderations on Modcls of I\1ovcment Det~ction

A general charaelerization of multi-input 1'1Ovcmcnt (!clt'ctioH . models is given in terms of tl.e Volterra series formalism. Wheil nonlinearities of order higher than the second arc ncgligibk, an II-input system can be decomposed into a sd of 2-input systems, summing lillearly. For a isymmdrical) 2-inpllt system which h;!s sigllifjcanlnonline:iri~ics only lip 10the second order, (he correlation modei is its most general expression. if the infinite time average of the output is taken. Specific obser,,::tions from optornolor expcri.nents (e.g. phase invari:IJI('e and contrast freqllcn';y dependence) can be interpreted in a gene. al way in lerr..s of propertil's of the Volterra representatiol1.