About the presenter: Greg Snyder married his high school sweetheart in their hometown of Charlotte, North Carolina, on May 31, 1997. Since then, they have moved east to Greenville NC, where he is currently a doctoral candidate of communication sciences and disorders at East Carolina University, and she is an interior designer. Greg's current hobby-de-jour is speaker building, while Courtney has a long-standing love for gardening and playing the violin. Together, they enjoy traveling, the outdoors, wildlife conservation, auto racing, and learning about vegetarianism from their two pet rabbits "Bunny" and "Mocha". Greg Snyder's professional website can be visited at www.elocutionary.com. Greg's picture was taken in Antarctica - the first Antarctic participant in the online conference! | |
Abstract
Recent technological advancements in digital processing and miniaturization have made an inconspicuous and truly wearable prosthetic fluency enhancing device a reality. This manuscript provides an explanation
of the fluency enhancing ASF phenomenon, and also discusses the prosthetic use
of ASF from various theoretical perspectives. While fluency enhancing prosthetic devices have the potential of fundamentally altering how the stuttering disorder is managed, existing research already suggests that ASF is not a cure-all. Thus, it is suggested that choosing
different types of stuttering managements is a personal decision based on the
unique values and treatment objectives of each individual person who stutters.
The Use of Speech Feedback in Stuttering Management
1. Introduction
Although
developmental stuttering is recognized as a chronic speech disorder with
behaviors that are lessened or even eliminated in certain speaking conditions
[4, 59, 66], a treatment offering the effortless elimination of stuttering
behaviors spanning an entire lifetime has yet to be discovered [4, 59]. The use of alternative treatments,
including prosthetic fluency enhancing devices -- either alone or combined with
other forms of stuttering management -- may be considered as an appealing
therapy alterative for some people who stutter [7, 58]. The purpose of this manuscript is to
discuss the research and clinical implications regarding the use of prosthetic
fluency enhancing devices in stuttering management.
2. Basic Theories of Stuttering Improvement
2.1 Endogenous and Exogenous Fluency Induction
A
condensed, and perhaps oversimplified, explanation of the fluency induction
phenomenon could propose that fluent speech can be temporarily produced in
those who stutter via two basic methods: one being endogenous (or
self-generated) changes in speech production, and another being exposure to
specific forms of exogenous (or external) speech feedback during
speech production [53, 59]. It has
been suggested that a common element within the numerous endogenous fluency
inducing techniques is the introduction of novel changes in speech production
[4], which appear to be associated with reductions in stuttering behaviors
[59]. Examples of endogenous
stuttering reduction methods may include speaking in a foreign accent, syllable
prolongations, easy vocal onsets, and other motorically-based speech therapies
[4, 55, 59, 66]. As endogenous
forms of fluency induction frequently appear to be associated with changes in
speech production [59], some of the resulting (fluent) post-therapeutic speech
has been documented as sounding unnatural [15, 23, 32, 50, 58], may require
large amounts of cognitive effort to maintain [7, 58] and also may be difficult
to apply consistently in real-word speaking situations [7, 8, 58]. Contrary to endogenous forms of
fluency induction, exogenous forms
use altered speech feedback (ASF), which has been documented to produce
immediately, albeit transitory, stable and natural sounding fluent speech in
those who stutter [1, 3, 32, 33].
Specifically, choral speech [CS; 4, 59], masked auditory feedback [MAF;
4, 27], delayed auditory feedback [DAF; 1, 4], frequency altered feedback [FAF;
20, 33], visual choral speech [VCS; 33, 56, 57], and delayed visual feedback
[DVF; 56, 57] have been documented to reduce stuttering behaviors immediately
by as much as 70 to 100% in some people who stutter [1, 33,
56]. The most efficient form of
fluency enhancing altered speech feedback appears to use a 'second speech
signal' [e.g., CS, DAF, FAF, VCS, DVF; 1, 33], which is a discrete speech
signal presented at the same time as the speaker's primary speech signal, and
contains speech gestures similar to those in the speaker's primary speech
signal. For the best fluency
enhancement, a second speech signal should be presented at the same time as the
speaker's primary speech signal, thereby simulating choral speech [1, 53]. (This effect is achieved either by
speaking in choral unison with another speaker, or from electronic alterations
of the speaker's primary speech signal, which are then reintroduced to the
speaker via headphones.) While exogenous
forms of stuttering reduction excel at instantly producing stable and natural
sounding fluent speech that requires significantly less cognitive effort than its endogenous
counterpart [7], research suggests that the effects of ASF cease immediately
when the speech feedback is stopped, and therefore has little, if any, carry-over of the fluency once the speech feedback has been removed
[1, 4].
2.2 Models of Stuttering and Altered Speech Feedback
With the absence of
a universally recognized 'cause' or 'cure' for developmental stuttering [4, 55,
59, 66], it may be pertinent to discuss the use of ASF from different
theoretical perspectives of the stuttering disorder. Since each theoretical perspective has its own distinct
position on the various supposed etiologies and treatments for stuttering, each
theoretical perspective also possesses unique attitudes and explanations of how
and why the ASF phenomenon reduces stuttering behaviors. As the immediate, yet temporary,
fluency enhancing effects of the ASF phenomenon have been repeatedly
demonstrated in a variety of speaking situations [1-4, 7-10, 19-20, 27-34,
40-41, 53, 57-63], further discussion regarding the use of ASF should not focus
on whether or not the phenomenon is effective, but instead focus on how this
technology should be integrated into existing stuttering managements, or if it
should be included at all. The
following is a cursory discussion of certain aspects within the behavioral and
neurolinguistic perspectives of stuttering, as they pertain to the ASF
phenomenon. It should be noted
that the two perspectives included within this manuscript were deliberately
selected and artificially polarized to better highlight the issues surrounding
the prosthetic implementation of ASF.
In reality, these perspectives often overlap and share commonalities, as they
both investigate the same disorder from differing points of view. Subsequently, the following discussion
should not be viewed as comprehensive or definitive; those seeking further
clarification or additional information should consider referring to the
stuttering literature for a more thorough account of the various perspectives
on developmental stuttering [4, 55, 59, 66].
2.2.1 Behavioral Paradigm
Most perspectives of
the stuttering disorder associated with the behavioral paradigm share the
principle that developmental stuttering most likely stems from some form of
speech-motor, or speech-coordination, dysfunction [4, 6, 12, 19-17, 21, 35-36,
42-43, 54, 55, 59, 64-66, 69-70 ].
This perspective may suggest that the symptoms of stuttering can be
reduced, if not potentially removed altogether, with corrective behavioral
compensations performed during speech production [54-55]. Individual perspectives within this
behavioral paradigm may also suggest that these corrective behavioral
compensations could eventually habituate, and become unconsciously integrated
into normal speech production, thereby greatly diminishing (or functionally
eliminating) stuttering behaviors in everyday speech [54-55]. The recognition of these fundamental
concepts becomes important, as certain points of view from within the
behavioral paradigm may have originally cited ASF (i.e., DAF) as reducing
moments of stuttering by behaviorally disrupting speech production, offering an
external source of rhythm, or slowing down the rate of speech [4]. Thus, if it is to be believed that ASF
induces fluency by initiating changes in motoric speaking behavior, then it
could be speculated that the use of ASF is unnecessary and redundant in the
treatment or management of stuttering, as the same results can be achieved
solely by behavioral methods.
Furthermore, this perspective may suggest that the use of ASF is
counterproductive in the treatment of stuttering, as it could deter clients
from becoming self-sufficient in the execution of their stuttering management
program.
2.2.2 Neurolinguistic Paradigm
While the
neurolinguistic perspective has yet to evolve into a single viewpoint that
shares a common set of unified principles accounting for the etiology and
treatment of developmental stuttering, this emerging paradigm does find
commonalities in the belief that the etiology of stuttering most likely lies
within functional neurological errors in speech preparation and/or sensory
motor integration—such as linguistic processing and encoding [11, 25-26],
sequential activation of linguistic planning and speech motor coding [51],
speech gesture initiation [56-57], or certain aspects of speech monitoring [45-49, 52]. This perspective may label stuttering
behaviors as a consequence of (or behavioral consequence to) the persistent neurolinguistic processing flaw
existing at the central (neurological) level [10, 56-57] that is the stuttering
disorder [10, 56-57].
Consequently, the neurolingustic point of view might suggest that
exposure to speech feedback (specifically in the form of a 'second speech
signal') may enhance fluency by modifying speech-related neural activation
patterns [5, 13-14, 22, 37, 44, 51-52, 67-68], which ultimately results in the execution of a
neurolinguistic speech-motor program that is more compatible with the
production of fluent speech [56-57].
Hypothesized restorative changes to the neurolinguistic processing may
include, but are not limited to, an inhibition of the stuttered response [53],
alterations of 'feedforward' and/or 'feedback' speech monitoring [45-49],
activation of the auditory cortices [33, 52], or potentially bypassing
endogenous speech gesture initiation altogether via an alternate premotor
system [18, 56-57]. Thus, certain perspectives within the neurolinguistic paradigm may suggest that the transient nature of the ASF phenomenon is a result of alterations within speech-related neurolinguistic processing, encoding, and/or programming that take place both instantly and in real-time, thereby potentially accounting for the lack of fluency enhancing carry-over effects associated with the ASF phenomenon. While exogenous
fluency enhancement (via speech feedback) lacks significant carry-over effects,
the resulting stable and natural sounding fluent speech may be interpreted to
suggest that ASF temporarily affects the etiology of the stuttering disorder
itself, rather than its symptoms or behavioral consequences.
2.2.3 Summary of Differing Paradigmatic Views
of Altered Speech Feedback
Developmental
stuttering is a very unique speaking disorder in that its symptoms are easily
reduced or even eliminated, at least temporarily, by both endogenous and
exogenous means. Those advocating
the endogenous management of developmental stuttering may cite hundreds of successful
behavioral treatment programs that have been documented over the past decades
[4], and assert that endogenous forms of stuttering management can produce
self-sufficient and successful results with time, effort, and practice [54-55]. The opposing view of primarily
endogenous forms of stuttering management may suggest that its post-therapeutic
speech often sounds unnatural, requires an unreasonable amount of cognitive
effort to use, suffers from an unreasonably high incidence of relapse, and may
never become automatic or habitual [7-9, 58]. Those supporting the prosthetic use of ASF will most likely
note the immediate, stable, natural sounding, and relatively effortless
enhanced fluency that the phenomenon produces [1-3, 7-9, 27-34, 53,
60-63]. However, individuals
challenging the prosthetic use of ASF may refer to research suggesting that the
fluency enhancement only occurs when the device is active and in use -- thereby
potentially creating a dependence on the prosthetic aid (as stuttering
behaviors will return if the prosthetic is removed), and also point out that
long-term effects (i.e., adaptation and relapse) regarding the daily prosthetic
use of ASF are untested.
3. Brief History of Altered Speech Feedback
3.1 Choral Speech
Stuttering research
has repeatedly demonstrated that when a person who stutters speaks in
(auditory) choral unison with other speakers, stuttering behaviors will be
drastically reduced, if not completely eliminated [1-3, 10, 27-34, 60-63]. In addition, research also suggests
that fluency is enhanced even if the choral 'second speech signal' is a
stuttered or non-fluent speech signal [31].
3.2 Masked Auditory Feedback
Stuttering research
has documented a consistent induction of fluency in those who stutter while
speaking under conditions of masking noise [1, 4], and appears to gain
efficiency and efficacy as the audible intensity of the masking noise rises
[4]. Thus, while auditory masking
is an effective fluency enhancer, it presents functional communicative
obstacles (i.e., potential hearing obstruction) and possible discomfort due to
the necessary intensity level auditory masking requires for significant fluency
enhancement.
3.3 Delayed Auditory Feedback
While delayed
auditory feedback has been documented as a significant fluency enhancer [1, 4,
27, 34, 61, 63], it may be pertinent to note that when DAF was discovered and
initially researched, a prevailing view at the time suggested that stuttering
was a behavioral speech disorder [4].
The initial explanations of DAF suggested that its fluency enhancing
powers were a result of gross changes in speech production [4], which -- in
hindsight -- probably can be associated with the extremely long delay in
auditory feedback (e.g., 250 milliseconds) rather than speech feedback itself. Later research suggested that a delay
as modest as 50 milliseconds was sufficient to enhance fluency in those who
stutter [34, 40, 60]. More recent
research suggests that the use of a shorter delay does not appear to
significantly alter speech production, and appears to enhance fluency
regardless of articulatory rate [34, 60-61].
3.4 Frequency Altered Feedback
The recognition of
frequency altered feedback (or 'frequency shifted feedback') as a significant
fluency enhancer [19, 20] was important in that it emphasized the concept that
fluency was evoked via a 'second speech signal,' rather than an auditory delay. FAF has been documented to provide
similar fluency enhancement to DAF [41]; combining DAF and FAF does not appear
to provide any significant fluency enhancement [41].
3.5 Visual Choral Speech
Visual choral speech
[33] (i.e. when a person who stutters speaks in unison with another speaker who
is silently mouthing, rather than audibly speaking) is significant in that it
evolved the concept of altered auditory feedback into altered speech
feedback [56-57]. While this
subtlety may initially appear to contribute little to the body of stuttering
research, the implications include elevating exogenous fluency induction beyond
the auditory sensory modality. This
recognition of visual choral speech (and the fluency inducing capabilities of
the visual sensory modality) is compelling some stuttering researchers to think
about fluency enhancement from a different perspective; instead of associating
exogenous fluency induction with the auditory sensory modality, researchers are
beginning to understand the importance of the commonalities found within the
speech signal, regardless of sensory modality, that may be sufficient to
enhance fluency in those who stutter.
3.6 Delayed Visual Feedback
The documentation of
fluency induction via delayed visual feedback [56] further supported the notion
that the fluency enhancement via speech feedback phenomenon is a multi-sensory,
rather that solely an auditory, phenomenon. While the ramifications of delayed visual feedback are still
being researched, research suggests that both synchronous and asynchronous
speech feedback enhances fluency regardless of sensory modality; DVF also
demonstrates the potential fluency enhancing effects of common invariant characteristics found
within the speech signal and speech production [56-57], such as the speech
gesture [38-39].
3.7 Summarizing Methodologies within Altered Speech Feedback
While many forms of
ASF have been documented to enhance fluency in those who stutter [1-3, 10,
19-20, 27-34, 41, 53, 56-57, 59, 60-63, 70], it has been suggested that ASF
using a 'second speech signal' is a more efficient fluency inducers [4, 33],
and therefore may be better candidates for prosthetic implementation. In addition, the 'second speech
signals' associated with the auditory modality are suggested to be inherently
easier to convert into a prosthetic device (such as a hearing aid) as opposed
to methodologies utilizing the visual modality. (While auditory second speech signals, such as DAF and FAF,
maybe the ideal candidates for prosthetic implementation, MAF may still be
useful for some people who stutter, especially those who are prone to inaudible
stuttering behaviors.) Although it
is unknown precisely why second speech signals are such efficient fluency
enhancers, early neurolingustic theories generally contend that
(externally-generated) choral speech (i.e., CS, VCS) may be a fundamental
component of the fluency enhancement via a second speech signal phenomenon;
other forms of (internally-generated) ASF (i.e., DAF, FAF, DVF) are theorized
to functionally emulate (externally-generated) choral speech via alterations in
the (internally-generated) second speech signal. Both synchronous (e.g., FAF) and asynchronous (e.g., DAF,
DVF) forms of speech feedback have been found to induce fluent speech in those
who stutter. Speech feedback has
been documented to produce natural sounding fluent speech that remains stable
in various speaking conditions, such as the telephone or in front of an
audience [2, 70]. ASF also has
been found to enhance fluency regardless of speech rate [19, 34, 41, 60-61],
and continue to enhance fluency even when introduced monaurally, rather than
binaurally [63]. While the ASF
phenomenon has been repeatedly documented to enhance fluency in those who
stutter, a single theory offering a commonly accepted explanation of the
phenomenon has yet to emerge. In
other words, despite the fact that ASF is documented as a significant fluency
enhancer, current research cannot sufficiently explain how and why the
stuttering behaviors are reduced.
4. Perspectives of the Prosthetic Implementation of ASF
4.1 Dependency on a Prosthetic Device
The
concern that a prosthetic fluency enhancing device would create dependency on
ASF rather than a form of self-sufficient stuttering management may depend on
how stuttering, as well as the daily consequences of stuttering behaviors, is
perceived. If developmental
stuttering is perceived as a behavioral disorder, then the use of an ASF
prosthetic device would be unnecessary, and potentially detract from the effectiveness of endogenous stuttering managements. Within this
perspective, some researchers or clinicians may suggest that an ASF prosthetic
device is an illusive short-cut towards immediate stuttering reduction; this
'quick-fix' may ultimately inhibit a direct confrontation with a long-term
self-sufficient (and self-reliant) solution to how stuttering is managed
because users may become dependent on a prosthetic device to reduce their
stuttering behaviors.
However,
if stuttering is perceived as a chronic error in neurolinguistic processing, then a prosthetic ASF device
could be perceived as a simple appliance that makes developmental stuttering
significantly easier to manage.
Furthermore, someone from this perspective may suggest that, despite
treatment, developmental stuttering remains a chronic disorder -- and like
every other chronic disorder (e.g., Arthritis; Asthma; Diabetes; Heart, Kidney
and Liver disease; Multiple Sclerosis; Parkinson's disease), it may require a
lifetime of constant (exogenous) management.
4.2 Personal Acceptance of Self and Stuttering
There is little
debate that the quality and enjoyment of life is associated with personal
acceptance [24]. Thus, if a
prosthetic ASF device is viewed as a crutch or an avoidance of stuttering
acceptance, then it would be tempting to suggest that such a device would
ultimately not be in the best interest for those in the stuttering
population. In other words, there
is a concern that the use of a fluency enhancing prosthetic device may prevent
its users from coming to terms with themselves (as persons who stutter) and
also their stuttering behaviors.
However, there is not enough research or empirical evidence to support
these notions; further testing and observation is needed. Furthermore, this perception assumes
that the quality of life and personal acceptance of the stuttering disorder are
directly related to stuttering severity -- a finding which research has yet to document[4].
4.3 Prosthetic Implementation of ASF is in its Infancy
Only with the recent
technological advancements in digital processing and miniaturization has an
inconspicuous and truly wearable prosthetic ASF device become a viable form of
stuttering management. There has not
been enough research or data to responsibly document the long term effects of
consistent exposure to the prosthetic implementation of ASF (in the form of a
second speech signal). This latter
point may be exceedingly pertinent, as customized prosthetic devices often
require a substantial financial investment. Even though this application of the ASF phenomenon shows
promise and may drastically alter how stuttering is managed, the long term consequences (both positive and negative) are currently unknown,
and currently being researched.
4.4 The Divisive Nature of Prosthetic Stuttering Managements
The development of
prosthetic fluency enhancing devices for the stuttering population may be
somewhat comparable to the development of cochlear implants for the deaf
community in that a single device may (at least partially) obscure the very
quality that creates the social minority.
However, since there is no universally recognized etiology or functional
'cure' for the disorder, it seems reasonable to suggest that stuttering
treatments should mirror the opinions, values, and therapeutic objectives of
each individual person who stutters.
Until a 'cure' for developmental stuttering is discovered, it is
sensible to offer those who stutter as many treatment options as possible, thereby
giving the stuttering population possibilities with which to manage stuttering
behaviors.
5. Conclusions
Without
a definitive treatment for developmental stuttering, the field of speech-language pathology
continues to serve the stuttering population by offering as many valid and
reliable treatments as possible; however, it is ultimately the client's
responsibility to become informed of the various approaches towards stuttering
management, and pick specific treatments that best meets their needs. While the prosthetic
implementation of ASF is compelling, research already suggests that it is a stuttering management, not a stuttering 'cure' [3]. With
this in light, the inclusion of a prosthetic ASF device into a stuttering
management program becomes a private choice that is determined by the personal
values and treatment objectives of each individual client.
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