To learn or not to learn: The growing paths of children’s phonological neighborhoods

To learn or not to learn: The growing paths of children’s

phonological neighborhoods

Yao Yao @berkeley.edu2009-1-11

1YY @ LSA Annual Meeting 2009

Overview

• Background• Data• Study 1• Study 2• Study 3• Discussion


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).


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)


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?


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)

YY @ LSA Annual Meeting 2009 6

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)


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


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


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


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


Preliminary counts


Study 1: size and average density of 3-phoneme words in children’s networks

• Size


• Average density

• Two children’s data overlayed (with Joel’s shifted by 2 stages)


Joel is probably more advanced than Ruth by 2 stages.

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.


Study 1: size and average density of 3-phoneme words in the local network

• Neighborhood density relative to vocabulary size


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


Study 2: neighborhood density of the same 3-phoneme words in TL

– Neighborhood densities in CL and TL are partially correlated (corr <0.4)


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


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?


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



• Average local density of 3-phoneme new vs. old words



• Average local density of 3-phoneme lost vs. retained words



• Before• Avg. density = 2


• After• Avg. density =

(4+6)*2/7=2.85


• Average density of 3-phoneme lost, new and old/retained words in the target language


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


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


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


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)


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) .


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


Acknowledgement

Child subjectsThe Manchester CorpusCHILDES databaseProf. Susanne GahlProf. Keith JohnsonAudience at the Berkeley Phonology Phorum


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, 205-215.

• Coady, J.A. & Aslin, R.N. (2003). Phonological neighborhoods in the developing lexicon. Journal of Child Language 30, 441-469.

• 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, 1-36.

• 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, 339-366.

• 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.


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), 1048-1058• Stager, C.L. & Werker, J.F. (1997). Infants listen for more phonetic detail in speech perception than in word-

learning tasks. Nature 388, 381-382.• Storkel, H.L. (2002). Restructuring of similarity neighbourhoods in the developing mental lexicon. Journal of

Child Language 29, 251-274.• Storkel, H.L. (2004). Do children acquire dense neighborhoods? An investigation of similarity neighborhoods

in lexicla acquisition. Applied Psycholinguistics 25, 201-221.• 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, 127-152.• 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.


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To learn or not to learn: The growing paths of children’s phonological neighborhoods