Proceedings of the Annual Meeting of the Cognitive Science Society

Phonological reduction and assimilation are intrinsic to speech. We report a statistical exploration of an idealised phonological version of the London-Lund Corpus and describe the computational consequences of phonological reduction and assimilation. In terms of intra- word information structure, the overall effect of these processes is to flatten out the redundancy curve calculated over consecutive segment-positions. We suggest that this effect represents a general principle of the presentation of information to the brain: information should be spread as evenly as possible over a representational surface or across time. We also demonstrate that the effect is partially due to the fact that when assimilation introduces phonological ambiguity, as in fat man coming to resemble fap man, then the ambiguity introduced is always in the direction of a less frequent segment: /p/ is less frequent than /t/. We show that this observation, the "Move to Markedness", is true across the board for changes in segment identity in English. This distribution of segments means that the number of erroneous lexical hypotheses introduced by segment-changing processes such as assimilation is minimised. We suggest that the Move to Markedness within the lexicon is the result of pressure from the requirements of a very efficient word recognition device that is sensitive to changes of individual phonological features.