*ABA effects in kinship allomorphy & syncretism

Morphological contiguity domains are pockets of natural language grammar wherein formal irregularity in one component predicts co-irregularity in a related, and often more marked, component. At the surface level, they foreclose certain allomorphic and/or distributional possibilities, producing so-called *ABA effects. Contiguity phenomena have been documented in the study of comparatives, case, pronouns, tense/aspect, inter multa alia. To this expanding list, this study adds kinship. It shall be shown that nonsingular pronouns in Lower Arrernte exemplify an apparent *ABA allomorphy-constraining distribution in which the agnate-disharmonic and non-agnate forms must co-supplete. An implementation using toy features demonstrates that the emergence of at least some *ABA patterns may be artifactual of how a paradigm is set up, and that Lower Arrernte nonsingulars do not instantiate Bobaljik (2012)'s containment hypothesis. These results are consonant with a picture of contiguity effects as a group of etiologically and derivationally heterogeneous phenomena, instead of an unambiguous diagnostic for syntactic hierarchical structure.