This thesis examines the learning and production of bound morphemes and how this linguistic behavior is influenced by the contextual predictability of the message those morphemes signal. Using the grammatical category of plurality (e.g. cup ~ cups) as a case study, and treating language as a system of message transmission, it demonstrates that the contextual predictability of a grammatical morpheme is correlated with variation in the learning and realization of that morpheme. Building on

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... s work examining the influence of contextual predictability on linguistic behavior at other levels of linguistic representation, this thesis suggests that a language user's knowledge of morphemes includes some representation of morphological predictability. This informs the larger question of what constitutes a language user's knowledge of language, and how linguistic behavior varies as a function of that knowledge. The influence of the contextual predictability of bound morphemes and the messages they signal is evaluated via three studies. These studies use the Rescorla-Wagner model and Message-Oriented Phonology, two frameworks which quantify the amount of information carried by a linguistic unit, to examine how the learning and production of bound morphemes is influenced by two biases that shape communication systems. These communicative biases are: a pressure to accurately transmit messages and a pressure to minimize resource costs. Study 1 explores the effects of morphological predictability on the learning of plural morphemes in an online artificial language learning experiment. Given multiple cues to the morphological category of plurality, this study shows that the second cue is learned less well when the message of plurality is more predictable, given first cue. Study 2 investigates gradient realizations of plural marking in a spoken corpus of New Zealand English. Using a measure of contextual predictability based on how often the preceding word occurs before a plural noun, this study shows that plural morphemes w [...]