A number of scholars have argued for the need to postulate principles of rule combination in morphological theory; according to such principles, two rules may combine to produce a more complex rule. Several kinds of evidence motivate the postulation of such principles, which afford new and revelatory explanations for a range of familiar morphological phenomena. Central to these explanations is a set of four characteristics (component independence, phonological transparency, semantic transparency, and domain subsectiveness) that combined rules possess by default but from which they may also deviate. This set of characteristics has both synchronic and diachronic significance. Synchronically, they elucidate the nature of potentiation, the relation between two affixes A and B such that stems created by means of A extend the domain of stems to which B may subsequently attach (Aronoff , Williams ). Diachronically, they illuminate the nature of affix telescoping, the diachronic correspondence of a sequence of two affixes at one stage in a language’s history to a single affix at a later stage (Booij , Haspelmath ). The evidence discussed here lends additional strength to the conclusion that principles of rule combination are a necessary addition to morphological theory.

This paper examines the emergence of a pattern that Stump and Finkel () dub Marginal Detraction: a tendency in inflection class systems for low type frequency (i.e., irregular) classes to disproportionately detract from the predictability of regular classes. We ask: What factors lead to the emergence (and sometimes non-emergence) of Marginal Detraction? We use an iterated agent-based Bayesian learning model to simulate the conditions for analogical restructuring of inflection classes over time. Input to the model consists of artificial inflection class systems that vary in how the classes overlap — their network structure. We find that network properties predict whether the Marginal Detraction distribution emerges within the model. We conclude that languagespecific network properties shape local interactions among words and thereby likely play a significant role in analogical inflection class restructuring and the emergence (or non-emergence) of global properties of inflectional systems.