  We adopt an evolutionary view on language change in which cognitive factors
(in addition to social ones) affect the fitness of words and their success in
the linguistic ecosystem. Specifically, we propose a variety of
psycholinguistic factors -- semantic, distributional, and phonological -- that
we hypothesize are predictive of lexical decline, in which words greatly
decrease in frequency over time. Using historical data across three languages
(English, French, and German), we find that most of our proposed factors show a
significant difference in the expected direction between each curated set of
declining words and their matched stable words. Moreover, logistic regression
analyses show that semantic and distributional factors are significant in
predicting declining words. Further diachronic analysis reveals that declining
words tend to decrease in the diversity of their lexical contexts over time,
gradually narrowing their 'ecological niches'.
