POISSON EVOLUTION IN WORD SELECTION

This paper presents the finding that the invocation of new words in hu man language samples is governed by a slowly changing Poisson process. The time dependent rate constant for this process has the form lambda (t) = lambda1(1 - lambda2t) e(-lambda2t) + lambda3 (1 - lambda4t) e(-l ambda4t) + lambda5, where lambda(i) > 0, i = 1,..., 5. This form impli es that there are opening, middle and final phases to the introduction of new words each distinguished by a dominant rate constant, or equiv alently, rate of decay. With the occasional exception of the phase tra nsition from beginning to middle, the rate lambda(t) decays monotonica lly. Thus, lambda(t) quantifies how the penchant of humans to introduc e new words declines with the progression of their narratives, written or spoken.