Plasticity, exemplars, and the perceptual equivalence of

‘defective’ and non-defective /r/ realisations

Rachael-Anne Knight& Mark J. Jones

1. Introduction

Perception of /r/ stimuli by subjects who use either ‘labiodental /r/’ [] or ‘apical /r/’ [].

No articulatory data here, acoustic terms:• labiodental /r/ = high F3, wide F2-F3 gap.• apical /r/ = low F3, narrow F2-F3 gap.

‘high F3’: F3 = F2 in surrounding vowels

Lab r outside articulatory continuum, acoustically distinct.

2. Developmental data

• /r/ mastered late by English speaking children (age 4;5+);

• acquisition pathway > > , though some data on [] and [] co-occurring;

• some adult speakers retain voiced labiodental approximant ;

• retention of infantile speech form = non-plasticity. Reasons for this unclear...

3. Why labiodental /r/?

• Research on non-arbitrary relationship between apical /r/ and labiodental /r/.

1) Sound change (actuation, not transmission)

2) Phonology of rhotics

3) Child/clinical phonology

4) Phonetic detail in phonological representations

3a. Phonetic detail

• Research indicates that perception is aided by phonetic detail;

• So representation may be detailed;

• Frequency of occurrence central:- influences representation

- representation influences production

• Lab /r/ - point on pathway to development

• Not most common - how abstract? why?

4. Production difficulties

• Number of gestures in /r/ (lips, tongue tip, tongue root).

• Vocal tract morphology.

• BUT [w] > [] is less complex (other reason for this sequence)

• WHY tongue tip?

• WHY co-occurrence of [] and []?

5. Perception difficulties

• Focus on acquisition of /w/ ~ /r/ contrast.

• BUT focus on /w/ - lack of phonetic acuity - [w]-like ≠ /w/.

• FURTHERMORE kids with [] have no problem with /r/ contrast.

• BUT does seem to explain /w/ in development pathway

6. Acoustic study

• Help to understand [] and [].• 5 subjects, all British English speakers.• Collected formant data (F1, F2 F3) for /r/, /w/

and /v/ at midpoint.• Phonetics of labiodentals - non-lingual,

superimposed on contextual lingual gestures. Important to keep same context (here //).

7. Results 1

• /w/ - as expected - low F1 and F2, high F3.• /v/ - as expected - minor deviation from F values

for flanking vowels.• /r/ - 2 patterns seen:

a) 4 subjects F2 for /r/ in-between /w/ and /v/;

b) 1 subject had F values very similar to /v/.

Only b) is TRUE labiodental /r/ (1/5).

7a. Results 1

/w/ /r/

7b. Results 1

/r/ /v/

8. Results 2

• F2 values around 1300 Hz for /r/ for 4 subjects

• suggest lingual gesture (but not raised tongue tip because of high F3).

• Why 4 subjects have low F2 if this causes perceptual conflict with /w/ in others and is due to (putative) lingual gesture?

9. Perceptual equivalence?

• Mid-frequency F2 equivalent to F2+F3 in apical /r/.

• Suggests that ‘labiodental’ /r/ users ignore F3 and match mid-frequency resonance.

• ‘Labiodental’ and apical /r/ are perceptually interchangeable (cf. child variation)?

10. Acoustic relationshipA

vera

ge

freq

uen

cy (

Hz)

Category

0

500

1000

1500

2000

2500

3000

‘labiodental’ /r/ apical approximant /r/

F3

F2

F1

F3

F2

F1

F2 in ‘labiodental’ /r/ corresponds to F2 + F3 in apical approximant /r/.

11. Perceptual test

• Aim was to find out if speakers with labiodental /r/ perceive differently to those with apical /r/

• Decided to construct pairs of VCV stimuli where consonant is some type of rhotic and ask both types of /r/ user whether consonants are same or different

12. Stimuli

• [ ] chosen = apical postalveolar approximant = labialised apical postalveolar approximant = labiodental approximant = velarised labiodental approximant = labial-velar approximant

• Recorded 10 tokens of each category• Each token rated for quality and best 2 chosen

from each category

13. Stimuli

• Each paired with ‘itself’ in ab (1 and 2) and ba (2 and 1) order

• Each token paired with every other in ab and ba order

• 80 ‘Different’ pairs presented 3 times (240)• 10 ‘Identical’ pairs presented 24 times

(240)

• = 480 pairs

14. Stimuli

• Pairs were concatenated in PRAAT

• Members of pair 1s apart

• ISI of 2s

• Each pair proceeded by a beep

• Gap of 10 seconds after each 20 pairs

• Gap preceded and concluded by 2 beeps

• About 45 minutes of stimuli

15. Subjects

• 10 subjects chosen from City and Cambridge student population

• 5 with apical /r/ (all female)

• 5 with labiodental /r/ (one male)

• Paid £5

16. Instructions

You will hear pairs of Vowel-Consonant-Vowel stimuli. Your task is to judge

whether the CONSONANTS in the pairs are IDENTICAL or DIFFERENT. Type

your response as i (identical) or d (different) in the Excel sheet provided, and

press the DOWN ARROW to the next field. If you are unsure whether or not the consonants in the stimuli are IDENTICAL

or DIFFERENT, please guess.

17. Procedure

• Subjects were given a practice run of 30 pairs– familiarise subject with task– check volume of recording

• Some subjects needed to start the practice several times

• After completing the practice, and ensuring instructions understood the test was begun

18. Overall errors

• Lab r users make more errors than apical users

• Lab r group = 329 errors (mean = 66)

• Apical group = 194 errors (mean = 39)

• t(8)=3.4, p<0.05 Lab r Apicalgroup

30.00

40.00

50.00

60.00

70.00

80.00

erro

rs

19. Errors on ‘different’ pairs

• Errors where ‘different’ pairs are labelled as ‘identical’

• Lab r = 199 errors (mean = 40)

• Apical = 131 errors (mean = 26)

• Note– [ ]– Apicals vs labdentals– [ ]

Pairs falsely labelled 'identical'

01020304050607080

ap v

rap

ap v

lab

ap v

vlab

ap v

w

rap

v lab

rap

v vla

rap

vs w

lab v

vla

lab v

w

vlab

v w

Type of errorN

um

be

r o

f e

rro

rs

lab

api

20. Errors on identical pairs

• Errors where ‘identical’ pairs are labelled as ‘different’

• Lab r = 132 errors (mean = 26)

• Apical = 58 errors (mean = 12)

• Note velarised labiodental approx

Pairs falsely labelled 'different'

0

10

20

30

40

50

apical r_apical labr vel_labr w

error type

Nu

mb

er o

f er

rors

lab

api

21. Experiment Conclusions

• Labiodental /r/ users, as a group, perform worse than apical /r/ users

• Labiodental /r/ users are more variable in their performance than apical /r/ users

• Both types of error occur suggesting some of the time subjects are guessing

• Lab r users are more likely to think that– apical and labiodental approximants are the same– two velarised labiodental approximants are different

22. Conclusions

• Data suggest that ‘labiodental’ /r/ has a principled relationship with apical /r/ based on mid-frequency resonance.

• Phonological representation develops gradually to include more temporal and spectral information: may be (and remain) quite abstract.

• Plasticity - Why change? Why fix?

Mark J. JonesDepartment of Linguistics

University of Cambridge

markjjones@hotmail.com

Rachael-Anne Knight

Department of Language and Communication Science

City University, London

knight@city.ac.uk