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Real World Constraints on the Mental Lexicon: Assimilation, the Speech Lexicon and the Information Structure of Spanish

Real World Constraints on the Mental Lexicon: Assimilation, the Speech Lexicon and the Information Structure of Spanish Words. Monica Tamariz Richard Shillcock monica@ling.ed.ac.uk rcs@cogsci.ed.ac.uk. Overview. Use information profiles of word systems (corpus, lexicons).

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Real World Constraints on the Mental Lexicon: Assimilation, the Speech Lexicon and the Information Structure of Spanish

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  1. Real World Constraints on the Mental Lexicon: Assimilation, the Speech Lexicon and the Information Structure of Spanish Words. Monica Tamariz Richard Shillcock monica@ling.ed.ac.uk rcs@cogsci.ed.ac.uk

  2. Overview • Use information profiles of word systems (corpus, lexicons). • More realistic representations of speech generate flatter profiles. • Flatter profiles reflect more efficient use of the representational space.

  3. Assumptions • Phonology plays a part in the organization of the mental lexicon. • For maximal efficiency, information should be spread as evenly as possible over the representational space.

  4. Distribution of information over the representational space

  5. Entropy • Concept of entropy from information theory (Shannon, 1948). • Measure of the uncertainty or information H = -  (pi · log pi) • Redundancy R = 1 - H

  6. Data sets • Speech corpus: 707,000 word tokens. • Speech lexicon: 42,000 word types. • Dictionary lexicon: 28,000 headwords.

  7. Transcriptions • Citation (30 phonemes) • Fast-speech (50 phonemes and allophones)

  8. Fast-speech transcription • Glides • Approximant B D G • Consonant assimilation e.g. [] [z] [dental n], [dental l]

  9. Transcriptions

  10. The Information Profile

  11. The Information profile Slope (-m) Mean level of entropy (Hrel)

  12. (Levelling effect of realistic representations) “Processes that make the representation of words more accurate will flatten the information profiles” The LERR principle

  13. The effect of the transcription:Information profile slopes • Fast speech has flatter profiles (as in other languages) • Longer words have flatter profiles

  14. The effect of the transcription: level of entropy. • More entropy in the citation transcription. • Fast speech is more redundant and thus, more predictable.

  15. The Speech Lexicon: Information profile slopes. • Speech Lexicon: the active mental lexicon represented in the brain. • The speech lexicon has flatter profiles.

  16. The Speech Lexicon:Level of entropy • Speech lexicon: low redundancy levels. • Level varies little across word lengths. • Support for Butterworth ‘Full Listing Hypothesis’.

  17. Corpus vs. Lexicon: Information profile slopes • Corpus: representation over time. • Lexicon: representation over space. • The lexicon yields flatter profiles.

  18. Corpus vs. Lexicon: Level of entropy. • The lexicon generates higher entropy levels.

  19. Discussion • Fast-speech rules and a ‘Full List’ mental lexicon flatten the information profile. • In the speech lexicon, the main constraint is efficiency of storage. • In the corpus, other constraints - such as lexical segmentation - interact with the optimization of communication.

  20. Conclusion • This simple analysis of the information profile of word systems is a useful tool that can provide insights into the validity of psycholinguistic theories.

  21. Real World Constraints on the Mental Lexicon: Assimilation, the Speech Lexicon and the Information Structure of Spanish Words. Monica Tamariz Richard Shillcock monica@ling.ed.ac.uk rcs@cogsci.ed.ac.uk

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