Transcript Document 7123109

Recent Models
of Stuttering
J. Scott Yaruss, Ph.D., CCC-SLP
University of Pittsburgh
Western Illinois University
February 7, 1997
Purpose
• To discuss two recent theoretical
models of stuttering
• Covert Repair Hypothesis
(Postma & Kolk, 1993)
• Neuropsycholinguistic Model
(Perkins, Kent, & Curlee, 1991)
Some Factors That May Be
Involved in Stuttering
Genetic
Linguistic
Environmental
Motoric
Psychological
Basic Steps in
Language Formulation
– Figuring out what you want to say
• Basic message
• Pragmatic intent
– Figuring out how you want to say it
•
•
•
•
Grammatical structure
Specific words
Sounds in the words
Prosody
Levelt’s (1989) “Blueprint for the Speaker”
CONCEPTUALIZER
discourse model,
situation knowledge,
encyclopedia
etc.
message
generation
monitoring
parsed speech
preverbal message
FORMULATOR
grammatical
encoding
surface
structure
SPEECHCOMPREHENSION
SYSTEM
LEXICON
lemmas
forms
phonological
encoding
phonetic plan
(internal speech)
phonetic string
ARTICULATOR
AUDITION
overt speech
Covert Repair Hypothesis (CRH)
(Postma & Kolk, 1993)
• Designed to explain the production of
speech disfluencies by adults who do
stutter as well as those who do not in
the context of general language models
• Based upon current psycholinguistic
models of speech production
(e.g., Dell, 1988; Levelt, 1989)
Theoretical Foundations
of the CRH—I
• Levelt’s “blueprint for the speaker”
– Describes conceptualization, formulation,
articulation, audition, and comprehension
– Explains how speakers monitor the accuracy and
appropriateness of their speech—both before and after
speech is produced
– Describes processes speakers can utilize to repair
detected errors in their phonetic plan by interrupting
ongoing speech (e.g., Levelt, 1983)
Levelt’s (1989) “Blueprint for the Speaker”
CONCEPTUALIZER
discourse model,
situation knowledge,
encyclopedia
etc.
message
generation
monitoring
parsed speech
preverbal message
FORMULATOR
grammatical
encoding
surface
structure
SPEECHCOMPREHENSION
SYSTEM
LEXICON
lemmas
forms
phonological
encoding
phonetic plan
(internal speech)
phonetic string
ARTICULATOR
AUDITION
overt speech
Levelt’s Monitoring Loops
CONCEPTUALIZER
MONITOR
preverbal message
INTERNAL
LOOP
parsed speech
SPEECH
COMPREHENSION
SYSTEM
FORMULATOR
phonetic plan
(internal speech)
phonetic string
ARTICULATOR
AUDITION
EXTERNAL
LOOP
overt speech
• Internal Loops
– In conceptualizer, before preverbal message is generated
– After phonetic plan is generated by formulator (covert speech)
• External Loop
– After speech is articulated (overt speech)
Theoretical foundations
of the CRH—II
• Dell’s (1988) Spreading-Activation Model of
Phonological Encoding
– Connectionist model
– Describes how phonological units are selected (and
mis-selected)
– When a node is activated at one level, activation
spreads to all connected nodes at other levels
– Node with highest degree of activation is selected
Connectionist Models
TACTIC FRAMES
LEXICAL NETWORK
SYNTACTIC LEVEL
S
NP
det
THE
CAT
VP
V
N
JUMP
N
Det
V
Past
Plural
N pl. V past
MORPHOLOGICAL LEVEL
WORD WORD WORD
THE
Sdet
Stem
Stem
CAT
Sdet
Af1
SN
–ED
JUMP
-S
Af2
SV
SN Af1 SV Af2
PHONOLOGICAL LEVEL
SYL
On
Rime
Nu
Co
k
æ
On
Nu
t
s
Co
Co
Spreading-Activation and
Phonological Errors
Morphological
Level
cap
cat
Direction of
Spreading Activation
downward
upward
Phonological
Level
k
æ
t
p
Basic Assumptions
of the CRH
• All speakers experience occasional
errors in their phonetic plan due to misselection of phonological units
• If errors are detected, they can be
repaired; repairs result in disfluencies
– Disfluencies are the by-product of
speaker’s attempt to repair phonetic plans
errors
Basic Assumptions
of the CRH (cont.)
• Individuals who stutter produce more
disfluencies because they are assumed to…
– have a slow phonological encoding mechanism
– attempt to begin speaking too soon or try to
speak too quickly for their impaired encoding
mechanism to make accurate selections
• The result is many phonetic plan errors
and many opportunities for disfluencies
Delayed Phonological Encoding
(after Yaruss & Conture, 1996)
TU = Target Unit
CU = Competing Unit
High
Activation
Level
TU
CU
Normal Activation
TU > CU
Low
0
time
Time of Selection
High
Activation
Level
Low
0
TU
CU
Delayed Activation
TU  CU
Time of Selection
time
What the CRH does and
does not attempt to explain
• Does attempt to explain
– The production of speech disfluencies in the
framework of normal language processes believed
to be exhibited by all speakers
• Does not attempt to explain:
– The developmental course of stuttering (e.g.,
repetitions prolongations, etc.)
– The development of accessory behaviors
(struggle, tension, etc.)
CRH Summary
• Speakers have the ability to monitor their speech— both
before and after it is produced
• Speakers sometimes make errors in phonological
encoding due to the spreading-activation mechanism
• If speakers detect these errors, they can interrupt speech
to repair them before they are produced
• The by-product of the interruption is a disfluency
• People who stutter produce more disfluencies because
their phonological encoding mechanism is assumed to be
impaired so there are frequent encoding errors
Neuropsycholinguistic Model
Perkins, Kent, & Curlee (1991)
• Speech involves many concurrent
language and motoric processes
• The timing of the interactions between
these processes is crucial
– This model, like the CRH, emphasizes timing,
but now we’re interested in timing between
language components
– Also called the “temporal dyssynchrony”
model
Neuropsycholinguistic Model
Perkins, Kent, & Curlee, 1991
Product of processing
high in awareness
Processing procedures low in awareness
Stress, intonation, duration, and vocal quality
PP SYSTEM
WORKING
MEMORY
SYSTEM
COGNITIVE SYSTEM
Formulation of ideas
LANGUAGE SYSTEM
Symbol System
Symbolic Mapping
prosody
SEGMENTAL SYSTEM
Phonetic Specifications
INTEGRATOR SYSTEM
Segments
Segments integrated into syllables
SPEECH MOTOR CONTROL SYSTEM
Syllable Slots
Integration of paralinguistic
and
prosodic components
Segment
order
Words for
phonemic analysis
Awareness
paralinguistic
Vocal signal system
Feeling and intent mapping
Assumptions of the
Neuropsycholinguistic Model
• Disfluencies occur due to a disruption
in timing between various linguistic
formulation and motoric execution
• Stuttering is defined as a “loss of
control” which occurs when the
individual is unable to continue
speaking, but does not know why
“Loss of Control”
• Some aspects of language formulation
are accessible to conscious awareness
• Others aspects (e.g., phonological
encoding, integration) are not
• Loss of control occurs when disruption
takes place in an aspect of the model
that is not “accessible”
One Unique Aspects of the Model
• Time pressure
– The pressure a speaker feels to continue
speaking when he is experiencing a
disruption in linguistic/motoric integration
– Increases the likelihood that the “loss of
control” feeling will occur
– Without abnormal time pressure, speech
disfluencies may occur, but stuttering will not
Summary of
Neuropsycholinguistic Model
• Speech requires integration of several
aspects of linguistic formulation with motoric
execution
• Processes can become disrupted
– If disruption is “accessible” to awareness, then a
disfluency will occur. If not, the speaker will
experience a loss of control
– If the loss of control is accompanied by abnormal
time pressure, stuttering will occur
?
?
What do these models tell
us about the diagnosis and
treatment of individual
people who stutter?
?
?
Not Much!
(yet)
However, the general language models
on which they are based can provide
guidelines about specific aspects of
language that should be examine in the
diagnosis of individuals who stutter
Levelt’s (1989) “Blueprint for the Speaker”
CONCEPTUALIZER
discourse model,
situation knowledge,
encyclopedia
etc.
message
generation
monitoring
parsed speech
preverbal message
FORMULATOR
grammatical
encoding
surface
structure
SPEECHCOMPREHENSION
SYSTEM
LEXICON
lemmas
forms
phonological
encoding
phonetic plan
(internal speech)
phonetic string
ARTICULATOR
AUDITION
overt speech
CONCEPTUALIZER
message
generation
monitoring
Conceptualization
• Basic Message
– Does client stutter more on complex messages?
– Does client stutter more on utterances with greater
propositionality or meaning?
• Pragmatic Intent
– How does social interaction affect fluency?
– Does client stutter more when experiencing
greater demands on pragmatic or social
interaction skills?
FORMULATOR
grammatical
encoding
surface
structure
phonological
encoding
Formulation
Grammatical Encoding
• Does client stutter more in situations which
require more complex utterances?
• Does client stutter more on syntactically
complex utterances?
• Does client demonstrate problems with
syntactic development which might interfere
with fluent speech production?
FORMULATOR
grammatical
encoding
LEXICON
lemmas
forms
phonological
encoding
Formulation
Lexical Access
• Does client exhibit word finding problems that
might interfere with speech production?
• Does client exhibit frequent mislabelings or
nonsystematic speech errors which might
interfere with fluent speech production?
• Are some words harder to retrieve than others?
FORMULATOR
grammatical
encoding
surface
structure
Formulation
Phonological Encoding
phonological
encoding
• Does client frequently produce nonsystematic
speech errors which might lead to production
self-repairs or speech disfluencies?
• Does client have difficulty retrieving the
phonological form of utterances (as in the “tip of
the tongue” phenomenon)?
FORMULATOR
phonological
encoding
phonetic plan
(internal speech)
Formulation
Phonological Development
ARTICULATOR
• Does client exhibit phonological delay which
might indicate a slow-to-develop linguistic
formulation system?
• Does client exhibit phonological delay which
makes communication more difficult and
increases sensitivity about his/her speech?
Articulation
• Does client stutter more when using a faster speaking
rate?
• Does client stutter more when leaving less time for
linguistic planning and formulation of utterances?
• Does client have difficulties with diadochokinetic
(DDK) abilities that might interfere with ability to
rapidly and precisely produce speech
Summary
• Several recent models of stuttering have
emphasized the role of language formulation
• These models are important for improving our
understanding of the nature of stuttering, in part
because of the research they encourage
• An increased understanding of the language
models on which these theories are based can
help us improve the diagnosis of stuttering