separation of co-occurring syllables: sequential and simultaneous grouping or can schemata overrule...

SEPARATION OF CO-OCCURRING SYLLABLES: SEQUENTIAL AND SIMULTANEOUS GROUPING

orCAN SCHEMATA OVERRULE PRIMITIVE

GROUPING CUES IN SPEECH PERCEPTION?

William J. Barry*, Georg Meyer** & Jacques Koreman*

* Institute of Phonetics, University of the Saarland, Saarbrücken, Germany

** Dept. of Communication and Neuroscience, Keele University, Keele, UK

29th European Mathematical Psychologists Group meeting (Keele, UK)28 August - 2 September 1998

OVERVIEW

• Introduction

• Primitives and schemata in ASA

• Double-vowel experiments

• Utterances

• Linguistic primitives and schemata

• Experiment 1

• Experiment 2

• Conclusions

PRIMITIVES AND SCHEMATA

SCHEMATA

PRIMITIVES

PRIMITIVES AND SCHEMATA

SCHEMATA

PRIMITIVES

• On- and offset (time domain)• F0 and harmonicity (frequency

domain)

DOUBLE VOWELS

SCHEMATA

PRIMITIVES

• F0 and harmonicity (frequency domain)

STYLISEDSPECTROGRAM

UTTERANCES

SCHEMATA?

PRIMITIVES?

LINGUISTIC PRIMITIVES

SCHEMATA

ACOUSTIC CUES

LINGUISTIC SCHEMATA

SYLLABLES

ACOUSTIC CUES

LINGUISTIC SCHEMATA

PHONOLOGICAL FEATURES

ACOUSTIC CUES

LINGUISTIC SCHEMATA (1)

/a:l/

PRIMITIVES

[alveolar] [nasal]

/e:n/

synthesised [a:l] synthesised [e:n]

LINGUISTIC SCHEMATA

/a:l/

PRIMITIVES

/e:n/

LINGUISTIC SCHEMATA (2)

/a:l/

PRIMITIVES

/e:n/

synthesised [a:l] synthesised [e:n]

EXPERIMENT 1

Stimuli: pairs of simultaneous synthetic VC syllables

/e://a://o:/

/l//n/

Subjects:10 German listeners who were able to identify more than 95% of the individual synthetic VC syllables correctly

EXPERIMENT 1

Task: identify the pair of synthetic VC syllables

/e://a://o:/

/l//n/

Primitives available to the listeners:

• 40-ms VC place transition with formants going from vowel to consonant target

• nasality cue starting early in vowel

EXPERIMENT 1

Phonetic background to the acoustic cues:

The place cue in the vowel transition has been shown to be more important for the perception of the consonant’s place of articulation than cues available in the consonant itself.

Nasality cues are very variable in speech production, varying strongly between languages and speakers, and should therefore be expected to play a less important role in perception.

place

nasality

EXPERIMENT 1

Task: identify the pair of synthetic VC syllables

pre-nas. Vpre-nas. V

non-nas. V non-nas. V

n

l n

l

consistent stimuli inconsistent stimuli

transtrans

Inconsistent stimuli were also presented in which

• the nasalised vowel was linked with /l/

• Non-nasalised vowel was linked with /n/

leading to conflicting nasality and place cues

BUT

pre-nas. cues

no pre-nas. cues

EXPERIMENT 1

Task: identify the pair of synthetic VC syllables

pre-nas. Vpre-nas. V

non-nas. V non-nas. V

n

l n

l

consistent stimuli inconsistent stimuli

correct

incorrect

transtrans

We say a VC pair is identified correctly if the place transitions are used for the decision. In the case of inconsistent stimuli this means that the nasality cue must be ignored!

NOTE

pre-nas. cues

no pre-nas. cues

EXPERIMENT 1

Question 1: Do listeners use the nasality cue?

EXPERIMENT 1

Question 1: Do listeners use the nasality cue?

Answer A: No.

Predicted experimental result:

No difference between consistent and inconsistent stimuli.

EXPERIMENT 1

Question 1: Do listeners use the nasality cue?

Answer A: No.

Predicted experimental result:

Consistent stimuli better identified than inconsistent ones.

Answer B: Yes.

EXPERIMENT 1

Question 1: Do listeners use the nasality cue?

consistent inconsistent

CONDITION

05

10

15

20

25

30

35

40

45

50% PAIRS CORRECT

Significant difference between consistent and inconsistent condition (p<0.01)

EXPERIMENT 1

Question 1: Do listeners use the nasality cue?

Answer A: No.

Corresponding experimental result:

Consistent stimuli better identified than inconsistent ones.

Whether listeners use nasality as a primitive or schema is unclear.

Answer B: Yes.

EXPERIMENT 1

Question 2: Do listeners map place cues onto phonetic feature schema?

EXPERIMENT 1

Question 2: Do listeners map place cues onto phonetic feature schema?

Answer A: No.

Predicted experimental result:

Given the identification rate of the vowel, the distinction in the identification of the consonant is above chance.

Reason: the acoustically different place transitions are used to link the vowel with the correct consonant in VC schema.

EXPERIMENT 1

Question 2: Do listeners map place cues onto phonetic feature schema?

Answer A: No.

Answer B: Yes.

Predicted experimental result:

Given the identification rate of the vowel, the distinction in the identification of the consonant is at chance level.

Reason: the acoustically different place transitions are mapped onto the same place schema (both cons. are alveolar) and cannot contribute to link the vowel with the correct consonant.

EXPERIMENT 1

Identification of VC pairs given correct vowel pair is at chance level

Question 2: Do listeners map place cues onto phonetic feature schema?

vowel pair correct

consistent inconsistent

CONDITION

010

20

30

40

50

60

70

80

90

100% PAIRS CORRECT

vowel pair correct

VC pair correct

VC pair correct

chance level VC pair correct, given correct vowel pair

EXPERIMENT 1

Question 2: Do listeners map place cues onto phonetic feature schema?

Answer A: No.

Answer B: Yes.

Corresponding experimental result:

Given the identification rate of the vowel, the distinction in the identification of the consonant is at chance level.

Reason: the acoustically different place transitions are mapped onto the same place schema (both cons. are alveolar) and cannot contribute to link the vowel with the correct consonant.

EXPERIMENT 1

CONCLUSIONS

• Listeners use acoustic continuity cues to link speech sounds: lower VC identification rate for inconsistent than for consistent stimuli shows that the nasality cue is used.

• Nasality cue may be a primitive or a schema.

• Listeners map the place-of-articulation primitives onto a schema: linking of the vowel with /n/ or /l/ is at chance level despite acoustically different place transitions, because the (phonetically important) place transitions are mapped onto the same schema for the two consonants.

EXPERIMENT 2

Stimuli: the same pairs of simultaneous synthetic VC syllables, but this time also at different F0’s

Subjects:10 German listeners who were able to identify more than 95% of the individual synthetic VC syllables correctly

EXPERIMENT 2

Task: identify the pair of synthetic VC syllables

Primitives available to the listeners:

• 40-ms VC place transition with formants going from vowel to consonant target

• nasality cue starting early in vowel

• F0

EXPERIMENT 2

Note: F0 provides “primitive” melody and harmonicity link between V and C

F0 cannot trigger a schema at the level of the stimulus offered for identification (VC syllable), although it may trigger a schema at higher levels of prosodic-phonological structuring, i.e. in intonation

EXPERIMENT 2

Question: Do listeners use the F0 cue more than they do nasality?

EXPERIMENT 2

Question: Do listeners use the F0 cue more than they do nasality?

Answer A: No.

Predicted experimental result:

Consistent stimuli better identified in the different-F0 condition, but distinction between consistent and inconsistent stimuli maintained or even enhanced.

EXPERIMENT 2

Question: Do listeners use the F0 cue more than they do nasality?

Answer A: No.

Predicted experimental result:

F0 cue overrides the distinction between consistent and inconsistent stimuli in the different-F0 condition.

Answer B: Yes.

EXPERIMENT 2

Question: Do listeners use the F0 cue more than they do nasality?

con incon20

25

30

35

40

45

50

55

60

same F0 different F0

% PAIRS CORRECT

con incon

Significant difference consistent/inconstent only for same F0 (p<0.01)

EXPERIMENT 2

Question: Do listeners use the F0 cue more than they do nasality?

Answer A: No.

Corresponding experimental result:

F0 cue overrides the distinction between consistent and inconsistent stimuli in the different-F0 condition.

Answer B: Yes.

EXPERIMENT 2

CONCLUSIONS

• F0 presents a strong continuation cue linking the V and C

• The F0 primitive cue overrides the nasality cue

very tentative... HYPOTHESES

• Primitives trigger schemata if possible

Place transitions in experiment 1 triggered same place schema and therefore could not override nasality cue.

Problem: we have no proof that nasality triggers a schema.

very tentative... HYPOTHESES

• Primitives trigger schemata if possible

Place transitions in experiment 1 triggered same place schema and therefore could not override nasality cue.

Problem: we have no proof that nasality triggers a schema.

• Competing primitives are weighted

In experiment 2, it is shown that the F0 primitive is a stronger cue than the inconsistent nasality cue.

very tentative... HYPOTHESES

• Primitives trigger schemata if possible

Place transitions in experiment 1 triggered same place schema and therefore could not override nasality cue.

Problem: we have no proof that nasality triggers a schema.

• Competing primitives are weighted

In experiment 2, it is shown that the F0 primitive is a much stronger cue than the inconsistent nasality cue.

Streams are preselected on the basis of F0

In experiment 2, the inconsistent nasality cue cannot be used by the listener because the F0 primitive has split the signal into two streams.

or

THANK YOU