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Tracking the timecourse of multiple context effects in assimilated speech. Bob McMurray Dept. of Brain and Cognitive Sciences University of Rochester. David Gow Massachusetts General Hospital. With thanks to Dana Subik, Joe Toscano & John Costalis . Laboratory Phonology. - PowerPoint PPT Presentation
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Tracking the timecourse of Tracking the timecourse of multiple context effects in multiple context effects in
assimilated speechassimilated speech David Gow
Massachusetts General HospitalBob McMurray
Dept. of Brain and Cognitive SciencesUniversity of Rochester
With thanks to Dana Subik, Joe Toscano & John Costalis
Overview
2) Coping with Coronal-Place Assimilation during online recognition.
Laboratory Phonology Spoken Word Recognition
1) Bridging fields yields:New solutions to old problems.New questions.
3) Implications for language processing & phonology.
Laboratory Phonology: How perceptual and articulatory constraints drive sound change and shape phonological systems
Bridging Fields: Laboratory Phonology
Rich information source in the signal: Constraints inferred through acoustic and articulatory measures.
Do phonological constraints inform word recognition?Can details of word recognition inform phonological constraints?
Perceptual models tend to come in two varieties:
Bridging Fields: Spoken Word Recognition
Spoken word recognition models that assume phonemic inputs as input to the lexicon and meaning.
Ignore systematic acoustic variation.
Phoneme perception models that relate acoustic properties to categorical perception
VOT0
100
PB
% /p/
ID (%/ pa/ ) 0
100Discrimination
Discrimination
VOT0
100
PB
% /p/
ID (%/ pa/ ) 0
100Discrimination
VOT0
100
PB
% /p/
ID (%/ pa/ ) 0
100
VOT0
100
PB
% /p/
ID (%/ pa/ ) 0
100
0
100Discrimination
Discrimination
Limits of categorical perception
Categorical perception (CP) is task-dependent, and doesnot appear to take place in tasks that involve spontaneous, naturalistic speech understanding.
McMurray, Aslin, Tanenhaus, Spivey & Subik (in prep)
Within category variation that should be lost in CP affectslexical processes
Andruski, Blumstein & Burton (1994), Gow & Gordon, 1995; Utman, Blumstein & Burton (2000), Dahan, Magnuson, Tanenhaus & Hogan (2001), Gow (2001; 2002; 2003)McMurray, Tanenhaus & Aslin (2003)
Speech perception and phonology relate signal properties to perception.
Systematic acoustic variation and SWR
Perc
ept
ion
Phonology
Meaning
Properties of the signal must be related to meaning—lexical activation.
Perception Ph
onol
ogy
Case study:
English Place Assimilation
English coronal place assimilation
/coronal # labial/ [labial # labial]
/coronal #velar/ [velar # velar]Prior work has treated this change as
• discrete• phonemically neutralizing
Assimilation
[ ]# berries nonword?
cat box?
cap box?[ ]# box
How are words recognized despite neutralization?
Phonological inference (Gaskell & Marslen-Wilson, 1996; 1998; 2001)
If [labial # labial] infer /coronal # labial/
greem beans green (Gaskell & Marslen-Wilson, 1996; Gow, 2001)
cap box cat (Gaskell & Marslen-Wilson, 2001; Gow, 2002)cap
Assimilatory modification is acoustically continuous.
Assimilation as Continuous Detail
F2 Transitions in /æC/ Contexts
Pitch Period155016001650
1700175018001850
Freq
uenc
y (H
z)
F3 Transitions in /æC/ Contexts
Pitch Period2550
2600
2650
2700
2750
2800
Freq
uenc
y (H
z)
coronalassimilatedlabial
Assimilation blends cues to two places of articulation
An Alternative View
Assimilation redistributes and blends information
cat box [# ]
Labiality of assimilatingitem
Coronality of assimilateditem
In theory: assimilation creates correlated cues…
[ # ]
Assimilating context might disambiguate blend
Blend might facilitate recognition of context
How can we determine if listeners use this information during recognition?
These questions require a method that:
• Measures lexical activation.• Sensitive to continuous acoustic detail.• Sensitive to temporal uptake of information.• Measures consideration of multiple items in parallel.
Visual World Paradigm
Visual World Paradigm
•Subjects hear spoken language and manipulate objects in a visual world.
•Visual world includes set of objects whose names represent competing hypotheses for the input.
•Eye-movements to each object are monitored throughout the task.
Tanenhaus, Spivey-Knowlton, Eberhart & Sedivy (1995)Allopenna, Magnuson & Tanenhaus (1998)
•Meaning based, natural task: Subjects
must interpret speech to perform task.
•Eye-movements fast and time-locked to speech—temporal dynamics.
•Fixation probability ~ lexical activation.
•Sensitive to within-category acoustic variability (McMurray, Tanenhaus & Aslin, 2003; Dahan, Magnuson, Tanenhaus & Hogan, 2001)
•Multiple competitors in same trial.
Present subjects with assimilated or non assimilated speech.
Measure activation for items that follow assimilation.
Experiment 1
Assimilation facilitates recognition.
Methods
Subject hears “select the maroon goose”“select the maroong goose”
Prediction: More fixations to goose after assimilated consonants.
34 Subjects. 16 sets of items. Subjects exposed to pictures/names before each block.
Stimuli cross-spliced from natural tokens—assimilation is not complete… continuous acoustic information.
“select the maroon duck”“select the maroon goose”“select the maroong duck” ***“select the maroong goose”
Spliced from “maroon duck”
Spliced from “maroon goose”
Eye-movements temporally aligned to onset of second word (goose or duck).
Target = Maroon GooseCompetitor = Maroon DuckUnrelated = Patriotic Duck and Goose
Time
200 ms Trials
1
2
3
4
5
… many more
trials
00.10.20.30.40.50.60.70.80.9
0 200 400 600 800 1000Time (ms)
Fixa
tion
Pro
port
ion Assimilated
Non Assimilated
0
0.1
0.2
0.3
0.4
0.5
0.6
0 100 200 300 400 500Time (ms)
Fixa
tion
Pro
port
ion
AssimilatedNon Assimilated
Results
Looks to the target (goose)
p = .03*
Looks to the competitor (duck)
0
0.05
0.1
0.15
0.2
0.25
0 200 400 600 800 1000
Time (ms)
Fixa
tion
Prop
ortio
n
Assimilated
Non Assimilated
Experiment 1: Summary
Continuous variation due to assimilation• not variability to be conquered… • signal to be used.
Assimilated coronals allow progressive operations.
• facilitate consistent targets• exclude inconsistent competitors earlier
Consistent with prior work using priming (Gow, 2001; 2003; Gow & Im, in press)
Lexical Ambiguity?
Even incomplete modification can create lexical ambiguity.
cat box catp box ?cat
cap
Does subsequent context regressively modify the interpretation of assimilated segments?
catp
box cat
p drawing
Experiment 2
Subject hears “select the cat
p box”“select the cat
p drawing”
Prediction:Fixations to cat or cap is a function of context.
0
0.1
0.2
0.3
0.4
0.5
0.6
0 400 800 1200 1600Time (ms)
Fixa
tion
Pro
port
ion
Coronal (cat)Non-Coronal (cap)
catp box Assim Non-Coronal
catp drawing Assim
Coronal
00.10.20.30.40.50.6
0 400 800 1200 1600Time (ms)
Fixa
tion
Pro
port
ion
Coronal (cat)Non-Coronal (cap)
Regressive effect is more biasing for non felicitous assimilation… perceptual locus?
?Progressive effects
too?
Regressive effects:Context biases interpretation of ambiguous token.
Will we see a progressive effect at the same time?
00.10.20.30.40.50.60.70.80.9
0 200 400 600 800 1000Time (ms)
Fixa
tion
Prop
ortio
n
Non-assimilatedAssimilated
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 200 400 600 800 1000Time (ms)
Fixa
tion
Prop
ortio
n
Non-assimilatedAssimilated
Target Competitor
Weaker effectsPossibly due to item
variability
Experiment 2: Summary
Assimilated coronals allow regressive operations:
• Context useful in resolving ambiguity.
Similar Progressive operations to experiment 1.
What kind of computation is responsible?
… relationship to continuous detail in signal important
Progressive & Regressive effects vary continuously across items.
Continuous Signal Continuous Response
Experiment 1: Progressive effect on target
-0.100
-0.050
0.000
0.050
0.100
0.150
0 2 4 6 8 10 12 14 16
Item #
Prog
ress
ive
Effe
ct
-0.3
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0 2 4 6 8 10 12 14 16
Item #
Reg
ress
ive
Effe
ct
Experiment 2: Regressive effect
What can the acoustics properties of these items tell us about perceptual variability?
Measured F1, F2, F3, Closure Duration of original items.
Regression:
F1, F2, F3, Closure
Interaction with Labiality.
Not enough power (items) to reach significance but model accounted for:
Experiment 1• Progressive effect: 75% of variance
Continuous acoustic variation is related to perceptual processes… how?
Experiment 2• Progressive effect: 57% of variance.• Regressive effect: 37% of variance
Feature cue parsing (Gow, 2003)
Time (s)0 0.760454
0
3000
[
A Perceptual Account
Feature cue parsing (Gow, 2003)
Time (s)0 0.760454
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3000
Any feature is encoded by multiple cues that are integrated
Feature cue parsing (Gow, 2003)
Time (s)0 0.760454
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3000
Feature cue parsing (Gow, 2003)
Time (s)0 0.760454
0
3000
Assimilation creates cues consistent with multiple places
Feature cue parsing (Gow, 2003)
Extract feature cues
Feature cue parsing (Gow, 2003)
Group feature cues by similarity and resolve ambiguity
Integration is by the same process within a segment.
Standard component of information integration in perception.
Feature cue parsing (Gow, 2003)
catp # box cat
p # drawing catp
# | | | |
[cor] [cor] [COR] [cor] [lab] [LAB] [lab] [lab]
example: cat….
catp # Box cat
p # Drawing catp #
| | [cor] [cor] [COR] [cor] [lab] [LAB] [lab] [lab]
Feature cue parsing (Gow, 2003)
Progressive and regressive effects fall out of grouping
example: cat….
Feature cue parsing based on basic perceptual grouping principles:
• Not specific to assimilation.
Parsing errors may lead to sound change:
• Pressure on languages to avoid errors
• Maximize contrast between adjacent segments.• Minimize juxtaposition of similar segments
Implications for Phonology
Feature parsing errors may lead to sound change
e.g. Shona Dissimilation (Ohala, 1981)
Pre-Shona
-b w a [LAB] [labio-velar glide]
Shona
-b a [LAB] (labio) [velar glide]
Gow & Zoll (2002)
Conclusions
English coronal place assimilation neutralizes phonemic distinctiveness.
Perceptual recovery cannot be based on symbolic processes.
Continuous perceptual mechanisms sensitive to systematic acoustic variation yield
•Progressive activation of upcoming material
•Regressive ambiguity resolution.Such mechanisms may play a role in sound change.
Bridging spoken word recognition and laboratory phonology helps both fields.
Conclusions
SystematicPhonological Variation
Perceptual Processes
Sound Change
Perceptual Processes
…
•In SWR: assimilation is not noise to be conquered, but signal to be used.
•In phonology: perceptual mechanisms for handling variation may constrain languages’ sound structures.