What motivates an inference?
The present article proposes both theoretical and empirical explanations for the semantic shift from the meaning temporal/spatial overlap to the meaning contrast/concessive, observable across genetically and geographically unrelated languages (e.g. English <i>while</i>, Japanese -<i>nagara</i>). The shift involves metonymic inference (Traugott & König 1991). However, our three experiments show that this inference is further motivated by a temporal/spatial overlap of two situations, which largely corresponds to perceptual overlap in Langacker’s viewing arrangement. Therefore, among Radden and Panther’s (2004) language-independent factors of motivation, perceptual motivation (perceptual overlap) is more fundamental to the semantic change in question than cognitive motivation (metonymic inference).