To learn or not to learn: The growing paths of children’s phonological neighborhoods Yao LSA Annual Meeting 2009

Overview Background Data Study 1 Study 2 Study 3 Discussion LSA Annual Meeting 2009

Phonological neighborhood (PN) General idea – The lexicon can be viewed as a network of words, in which similar-sounding words are connected to form phonological neighborhoods. – Defining neighbors One-phoneme difference rule (Luce & Pisoni, 1998). LSA Annual Meeting 2009 cat kit mat cap map cape mop it

Evidence for PN Speech perception – Inhibitory effect (Luce & Pisoni, 1998) Speech production – Facilitative effect (Vitevitch, 2002) – Hyperarticulation (Munson & Solomon, 2004) 4 LSA Annual Meeting 2009

Children’s PN development Start small and sparse (Charles-Luce & Luce, 1990; Logan, 1992; Storkel, 2002) How do children’s phonological neighborhoods grow? – From the target language (TL) perspective Early acquired words are short in length, high in frequency and from dense neighborhoods in TL (Storkel, 2004) – From the local child language (CL) perspective Acquire similar-sounding words? Acquire dissimilar-sounding words? LSA Annual Meeting 2009

Puzzle Perceptual abilities – Infants at a very young age can perceive fine phonetic detail (Aslin, Jusczyk & Pisoni, 1998) Used in word learning ? – Children have difficulty in learning similar- sounding novel words (Stager & Werker, 1997) – Children are sensitive to the phonetic detail in the input. (Zamuner, 2006, 2009; Coady & Aslin, 2003) LSA Annual Meeting 20096

Two models LRM (Lexical Restructuring Model; Metsala & Walley, 1998) – Holistic lexical representations initially. More detailed phonemic representation is necessitated as the vocabulary grows. PRIMIR (Processing Rich Information from Multidimensional Interaction Representations; Werker & Curtin, 2005) – “phonetic detail is incorporated into early lexical representations” (Zamuner, 2009:7) LSA Annual Meeting 20097

Examining PN development If holistic representation… – Acquire dissimilar-sounding words – Avoid dense neighborhoods If detailed phonetic representation… – Acquire similar-sounding words – Form dense neighborhoods Influence from the TL LSA Annual Meeting 20098

Database From the Manchester corpus in CHILDES database (Theakston, et al., 2001; MacWhinney, 1991) – Two monolingual British children Joel [1;11- 2;10] “word learner“ (Ke & Yao, 2008) Ruth [2;0 - 2;11] “grammar learner“ (Ke & Yao, 2008) – 1-year longitudinal study – 34 recordings, 1hr each, approx. 1 per 10 days LSA Annual Meeting 2009

Stage division (Ke & Yao, 2008) – 0.5 increase in MLU (Mean Length of Utterance) per stage – 5 recording sessions – 40 days – Non-overlapping – Joel S1, S2, S3, S4a, S4b, S5 – Ruth S1, S2, S3a, S3b, S4, S5 LSA Annual Meeting 2009

Network model Input –Spontaneous speech of the child –Phonetic transcription is obtained from the CELEX database. –No regular inflected forms or contracted forms if the base forms already exist Neighborhood definition –One-phoneme difference rule LSA Annual Meeting

Preliminary counts LSA Annual Meeting 2009

Study 1: size and average density of 3- phoneme words in children’s networks Size LSA Annual Meeting 2009 Average density

Two children’s data overlayed (with Joel’s shifted by 2 stages) LSA Annual Meeting 2009 Joel is probably more advanced than Ruth by 2 stages. Study 1: size and average density of 3- phoneme words in children’s networks

Study 1: size and average density of 3- phoneme words in the local network Q: is the increase in density an artifact of the increase in lexicon size? Coady & Aslin (2003) – Calculate neighborhood density as a proportion of the entire lexicon, not in raw counts of neighbors. LSA Annual Meeting

Study 1: size and average density of 3- phoneme words in the local network Neighborhood density relative to vocabulary size LSA Annual Meeting 2009

Study 1: Discussion Absolute number of neighbors increase over time When lexicon size is normalized, neighborhood density – Increases in Ruth’s early stages – Slightly decreases in Ruth’s late stages and all Joel’s stages LSA Annual Meeting 2009

Study 2: neighborhood density of the same 3-phoneme words in TL – Neighborhood densities in CL and TL are partially correlated (corr <0.4) LSA Annual Meeting 2009

Study 2: Discussion Average neighborhood density (in adult lexicon) – Increases in Ruth’s early stages – decreases in Ruth’s late stages and all Joel’s stages Joel’s development is probably two stages more advanced than Ruth LSA Annual Meeting 2009

Study 3 Assumptions – Word learning as a dynamic process Acquire words Lose words – Stage networks represent the lexicon of the child at that stage Q: What words are acquired, lost, and kept? Hi-density words or low-density words? LSA Annual Meeting

Study 3: What words are acquired, lost and kept? New vs. old words – New words: words that don’t exist in the previous lexicon – Old words: words that already exist in the previous lexicon Lost vs. retained words – Lost words: words that don’t exist in the next lexicon – Retained words: words that still exist in the next lexicon Old/ Retained New Lost S1 lexicon S2 lexicon LSA Annual Meeting 2009

Study 3: What words are acquired, lost and kept? Average local density of 3-phoneme new vs. old words LSA Annual Meeting 2009

Study 3: What words are acquired, lost and kept? Average local density of 3-phoneme lost vs. retained words LSA Annual Meeting 2009

Study 3: What words are acquired, lost and kept? Before Avg. density = 2 LSA Annual Meeting 2009 After Avg. density = (4+6)*2/7=2.85

Study 3: What words are acquired, lost and kept? Average density of 3-phoneme lost, new and old/retained words in the target language LSA Annual Meeting 2009

Study 3: Discussion In Ruth’s early stages – Newly-acquired words are structurally MORE important than existing words – Structurally-important words are MORE susceptible to being lost In Ruth’s late stages and all Joel’s stages – Newly-acquired words are structurally LESS important than existing words – Structurally-important words are LESS susceptible to being lost LSA Annual Meeting 2009

General Discussion In early stages of lexical acquisition – acquire words that sound similar to existing ones and increase local density – build up the backbone of the phonological network by adding important nodes – important words are also easier to lose After that – words that are acquired are less important – important words are less likely to be lost LSA Annual Meeting 2009

Implications Pressure to form/deform denser neighborhoods coexist in early stages Perceptual abilities – Probably used from the early stage of word learning PRIMIR model – Stabilize after a while LSA Annual Meeting

Implications Critical mass hypothesis – after the lexicon exceeds a critical size, qualitative changes in linguistic performance and/or acquisition strategy will take place (Marchman & Bates, 1994) Critical size – ~200 words – cf. Vogel Sosa & Stoel-Gammon (2006) LSA Annual Meeting 2009

Complications Token frequency – Neighborhood density in CL is partially correlated with token frequency in child speech (cor < 0.45) and maternal input (cor <0.45). LSA Annual Meeting

Caveats Sampling frequency – 5hrs recording spread over ~40 days – Is the stage lexicon a decent representation of the child’s productive lexicon? – Is the division of new/old, lost/retained words fair enough? Phonological network model – The use of dictionary pronunciation of words – Definition of neighbors – Different types of neighbors LSA Annual Meeting

Acknowledgement Child subjects The Manchester Corpus CHILDES database Prof. Susanne Gahl Prof. Keith Johnson Audience at the Berkeley Phonology Phorum LSA Annual Meeting

Selected references Aslin, R.N., Jusczyk, P.W. & Pisoni, D.B. (1998). Speech and auditory processing during infancy: constraints on and precursors to language. In D. Kuhn & R. Siegler (eds), Handbook of child psychology: cognition, perception and language, vol. 2, NY: Wiley. Charles-Luce, J. & Luce, P.A. (1990). Similarity neighborhoods of words in young children’s lexicons. Journal of Child Language 17, Coady, J.A. & Aslin, R.N. (2003). Phonological neighborhoods in the developing lexicon. Journal of Child Language 30, Logan, J.S. (1992). A computational analysis of young children’s lexicons (Tech. Rep. No. 8). Bloomington, IN: Speech Research Laboratory, Dept. of Psychology, Indiana Univ. Luce, P.A. & Pisoni, D.B. (1998). Recognizing spoken words: the neighborhood density activation model. Ear and Hearing 19, MacWhinney, B. (1991). The Childes Project: Tools for Analyzing Talk. Lawrence Erlbaum Associates. Marchman, V.A. & Bates, E. (1994) Continuity in lexical and morphological development: a test of the critical-mass hypothesis. Journal of Child Language 21, Metsala, J. L. & Walley, A. C. (1998). Spoken vocabulary growth and the segmental restructuring of lexical representations : Precursors to phonemic awareness and early reading ability. In J. L. Metsala & L. C. Ehri (eds), Word recognition in beginning literacy, 89–120. New York: Erlbaum. LSA Annual Meeting

Selected references Munson, B. & Solomon, N.P. (2004). The effect of phonological neighborhood density on vowel articulation. Journal of Speech, Language, and Hearing Research 47(5), Stager, C.L. & Werker, J.F. (1997). Infants listen for more phonetic detail in speech perception than in word-learning tasks. Nature 388, Storkel, H.L. (2002). Restructuring of similarity neighbourhoods in the developing mental lexicon. Journal of Child Language 29, Storkel, H.L. (2004). Do children acquire dense neighborhoods? An investigation of similarity neighborhoods in lexicla acquisition. Applied Psycholinguistics 25, Theakston, A. L., Lieven, E. V. M., Pine, J. M., & Rowland, C. F. (2001). The role of performance limitations in the acquisition of verb-argument structure: an alternative account. Journal of Child Language 28, Vitevitch,. (2002). The influence of phonological similarity neighborhoods on speech production. Journal of Experimental Psychology: Learning, Memory, and Cognition 28(4), 735–747. Vogel Sosa, A. & Stoel-Gammon, C. (2006). Patterns of intra-word phonological variability during the second year of life. Journal of Child Language 33, 31–50. Werker, J. F. & Curtin, S. (2005). PRIMIR: A developmental framework of infant speech processing. Language Learning and Development 1, 197–234. Zamuner, T. S. (2006). Sensitivity to word-final phonotactics in 9- to 16-month-old infants. Infancy 10, 77–95. LSA Annual Meeting