Computational locality in morphological maps

Abstract

This paper presents a computational investigation of a range of morphological operations. These operations are first represented as morphological maps, or functions that take a stem as input and return an output with the operation applied (e.g., the ing-suffixation map takes the input ‘dɹɪŋk’ and returns ‘dɹɪŋk+ɪŋ’). Given such representations, each operation can be classified in terms of the computational complexity needed to map a given input to its correct output. The set of operations analyzed includes various types of affixation, reduplication, and non-concatenative morphology. The results indicate that many of these operations require less than the power of regular relations (i.e., they are subregular functions), the exception being total reduplication. A comparison of the maps that fall into different complexity classes raises important questions for our overall understanding of the computational nature of phonology, morphology, and the morpho-phonological interface.