neural correlates of gated word recognition

Neural Correlates of Gated Word Recognition in Bilinguals and Monolinguals

Derick D. Deweber, MS, CCC-SLPFrank R. Boutsen, PhD, CCC-SLP

2009 ASHA Convention New Orleans, LA

Presentation Overview

• Review of models of word recognition• Discussion of first bilingual word recognition

study• Discussion of pilot EEG study• Future directions

Word Recognition in Monolinguals

• Methods used to examine spoken word recognition

• Findings from studies on word recognition

• Models of spoken word recognition

Experimental Methods• Lexical decision

• Subject required to make decision based on stimulus; could be affected by word status, word frequency, and context

• Priming• Subject makes decision following two words that may be related or unrelated

(i.e., semantic priming) or may inform subject which language to use• Shadowing

• Subject required to repeat back word as they hear it; words may contain semantically unpredictable errors

• Gating• Subject makes decision about word after hearing increasing increments of a

target word

Experimental findings• Word frequency effects

• More frequent words recognized faster than non-frequent words• Word supremacy effects

• Target recognized more easily when it is a word; non-words less easily recognized

• Context effects• Words are more easily recognized in context than when they

occur alone• Distortion effects

• Words are more easily recognized when distorted at the end than if distorted at the front

Models of Word Recognition

• Initial Cohort Model

• Neighborhood Activation Model (NAM)

Initial Cohort Model

• Marslen-Wilson, 1990• As initial phonemes of a word are heard, all words in the

lexicon that share these phonemes are activated• Words that share phonemes and that are

simultaneously activated are called a “cohort”• As more of the spoken word unfolds over time the

relative size of the word’s cohort diminishes• This process unfolds until the target word is recognized

Neighborhood Activation Model (NAM)

• Luce, Pisoni, & Goldinger, 1990• “Goodness of fit” model where word is identified

based on fit of stimulus and features of alternatives (Connine, Blasko, & Titone, 1993)

• Density of word’s “neighborhood” is based on shared phonemes of word and other words as well as the frequency of the words neighbors

• Does not account for prosodic sensitivityFrequency -

Gating Paradigm in WR Research

• Wingfield et al., 1997• Found that when a word is constrained by stress, cohort

size is a better predictor of when the word will be recognized than when stress pattern is ignored

• Lindfield, Wingfield, and Goodglass, 1999• Found that words were correctly recognized with much

less segmental (initial cohort) onset information when word prosody was available to subjects

Experiment 1

• Application of gating paradigm established by Lindfield, Wingfield, and Goodglass, 1999

• the effect of prosody on word recognition in adult speakers of English,

early bilingual (Spanish/English) late bilingual (Spanish/English)

• How does English “accent” affect word recognition scores?

ParticipantsGroup 1English Monolinguals

Group 2Early Bilinguals

Group 3Late Bilinguals

Age

Gender

40.2 years (12.57 SD)4 M - 6F

32.5 years (15.39 SD)1 M - 7 F

37.8 years (8.80 SD)1 M - 9 F

Age Began Speaking English

From Birth6.5 years (1.60 SD)

29 years (5.68 SD)

Time Speaking English

From Birth 26 years (14.83 SD)

11 years (6.83 SD)

Materials

• 30 English words• 12 two-syllable

• 6 with stress on 1st syllable• 6 with stress on 2nd syllable• Ballet, diamond, dolphin, penguin, pumpkin, sparrow, window, cartoon,

exhaust, guitar, quartet, hotel• 18 three-syllable

• 6 with stress on 1st syllable• 6 with stress on 2nd syllable• 6 with stress on 3rd syllable• Celery, photograph, pineapple, radio, stadium, telescope, apartment,

cathedral, foundation, horizon, umbrella, suspender, chandelier, engineer, gasoline, kangaroo, referee, violin

• All words are common nouns with a mean frequency of 37 words per million in print (Francis & Kucera, 1982)

• Spoken with carrier phrase “The word is” with normal intonation by a female speaker of American English

• Words were digitized and later manipulated in Audacity and Praat sound software applications

• Target words began at 50 ms gate size and increased incrementally by 50 ms

• Gated stimuli were presented in 3 conditions1. Onset only2. Onset plus duration3. Onset plus prosody

Onset Only50 ms gate

100 ms gate

150 ms gate

200 ms gate

250 ms gate

300 ms gate

350 ms gate

400 ms gate

450 ms gate

500 ms gate

Onset plus Duration50 ms gate

100 ms gate

150 ms gate

200 ms gate

250 ms gate

300 ms gate

350 ms gate

400 ms gate

450 ms gate

500 ms gate

Onset Plus Prosody50 ms gate

100 ms gate

150 ms gate

200 ms gate

250 ms gate

300 ms gate

350 ms gate

400 ms gate

450 ms gate

500 ms gate

Procedure

• Each subject heard all 30 words (10 from each condition)

• Words presented in increasing increments of 50 ms beginning with the first presentation at 50 ms

• Procedure continued until subject correctly identified word

• Words were blocked by condition, with conditions being counter-balanced across subjects

Results

Group Onset Only Onset + Duration

Onset + Prosody

English Monolinguals

323.5 (112.02)

359 (163.36) 283 (158.94)

EarlyBilinguals

349.38 (113.21)

370.63 (164.72)

360.63 (158.85)

LateBilinguals

415.5 (121.98)

402.5 (139.33)

412.9 (133.39)

Onset Only

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English Only

Early Bilingual

Late Bilingual

Onset + Duration

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Onset + Prosody

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Early Bilingual

Late Bilingual

Experiment 2

• Same paradigm as experiment 1

• Speaker with Spanish accent

• How does Spanish “accented” English affect word recognition scores?

ParticipantsGroup 1English Monolinguals

Group 2Early Bilinguals

Group 3Late Bilinguals

Age

Gender

40.2 years (12.57 SD)4 M - 6F

32.5 years (15.39 SD)1 M - 7 F

37.8 years (8.80 SD)1 M - 9 F

Age Began Speaking English

From Birth6.5 years (1.60 SD)

29 years (5.68 SD)

Time Speaking English

From Birth 26 years (14.83 SD)

11 years (6.83 SD)

Materials

• 30 English words• 12 two-syllable

• 6 with stress on 1st syllable• 6 with stress on 2nd syllable• Atom, chicken, cotton, football, harbor, magic, award, debate,

expense, remark, routine, affair• 18 three-syllable

• 6 with stress on 1st syllable• 6 with stress on 2nd syllable• 6 with stress on 3rd syllable• Accident, artery, camera, funeral institute, graduate, assistant,

composer, dependent, detective, formation, illusion, magazine, questionnaire, cigarette, personnel, volunteer, refugee

• All words are common nouns with a mean frequency of 36.43 words per million in print (Francis & Kucera, 1982)

• Spoken with carrier phrase “The word is” with normal intonation by a female speaker of American English with a Spanish accent

• Words were digitized and later manipulated in Audacity and Praat sound software applications

• Target words began at 50 ms gate size and increased incrementally by 50 ms

Procedure

• Each subject heard all 30 words (10 from each condition)

• Words presented in increasing increments of 50 ms beginning with the first presentation at 50 ms

• Procedure continued until subject correctly identified word

• Words were blocked by condition, with conditions counterbalanced across subjects

• Gated stimuli in Experiment 2 were also presented in 3 conditions

1. Onset only2. Onset plus duration3. Onset plus prosody

Onset Plus Prosody50 ms gate

100 ms gate

150 ms gate

200 ms gate

250 ms gate

300 ms gate

350 ms gate

400 ms gate

450 ms gate

500 ms gate

Results

Group Onset Only Onset + Duration

Onset + Prosody

English Monolinguals

447 (119.73) 465.5 (140.47)

398 (127.51)

EarlyBilinguals

363.75 (95.80)

394.38 (121.43)

338.75 (112.22)

LateBilinguals

360 (111.24) 387 (130.77) 342 (113.87)

Onset Only

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English Only

Early Bilingual

Late Bilingual

• =Onset + Duration

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Discussion

• Prosody contributes to the recognition of spoken words• Experiment 1: Monolingual vs. Late (t=1.9797, df=18, p=.0632)• Experiment 2: Monolingual vs. Late (t=1.0359, df=18, p=.3140)

• Addition of Spanish-accent to spoken English words delays word recognition in native speakers of English

• Prosodic mismatch? Not unlike Phonological Mismatch (Imai, Flege, and Walley, 2003)

• Degree of fluency in second language likely affects how words are stored and accessed

• Age of SLA also likely contributor to success in word recognition

Pilot Study

• Application of gating procedure to EEG paradigm

• To investigate functional differences that may exist been monolinguals and late bilinguals in terms of how and when prosody is used in the brain to assist with word recognition

Participants

• 7 English Monolinguals (from in and around greater OKC area)

• 7 Spanish-English Late Bilinguals (originally from Mexico; began learning English after the age of 18)

• All participants reported to have no know neurologic impairment, speech and/or hearing difficulties, or other confounding medical condition

Materials

• 50 two syllable and 50 three syllable words• All words are common nouns with a mean frequency of

38 words per million in print (Francis & Kucera, 1982)• Words were digitized and later manipulated in Audacity

and Praat sound software applications• Words filtered at 325 hz and gated with prosodic

information only• Target words began at 100 ms gate size and increased

incrementally by 300 ms

Procedure

• Participant is connected to Nicolet version 5.3 EEG analysis unit according to international 10-20 system with waves collected at 19 electrode sites (fp1, fp2, f7, f8, t3, t4, t5, t6, 01, 02, f3, f4, c3, c4, p3, p4, fz, cz, pz)

• Participants instructed to minimize facial movements, eye blinks, swallows, etc

• Each participant hears all five gates (100, 150, 200, 250, 300 ms) of each of the 100 target words

• Participants are encouraged to only respond to gate only when they feel that they know what the word is

• Example:

100 250 300 150 200

Early Behavioral Results

Group Mean Gate SizeEnglish

Monolingual238.86 (55.5)

Spanish-English Late Bilingual

226 (49.71)

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2

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100 150 200 250 300

Group 1

Group 2

F

P

T

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Normal controlLeft Right

F

P

T

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Normal controlLeft Right

Next Steps

• Deal with obstacles to this paradigm• Further data analysis• Possibly investigate word frequency effects

and/or accent effects on word recognition between the two groups (in terms of event related potentials)

For more information

OUHSC Department of Communication Sciences and Disorders

1200 N Stonewall

Oklahoma City, OK 73126

(405) 271-4214

Derick-Deweber@ouhsc.edu

Frank-Boutsen@ouhsc.edu