A relaxed admixture model of contact
Under conditions of language contact, a language may gain features from its neighbors that it is unlikely to have gained endogenously. We describe a method for evaluating pairs of languages for potential contact by comparing a null hypothesis, in which a target language obtained all its features by inheritance, with an alternative hypothesis in which the target language obtained its features via inheritance and via contact with a proposed donor language. Under the alternative hypothesis, the donor may influence the target to gain features, but not to lose features. When applied to a database of phonological characters in South American languages, this method proves useful for detecting the effects of relatively mild and recent contact, and for highlighting several potential linguistic areas in South America.