Training Slow Speaking Rate to
Treat Motor Speech Disorders
Authors: Laura Clinton
Greg Turner, Ph.D., CCC-SLP
Robert de Jonge, Ph.D., CCC-A
INTRODUCTION
Motor speech disorders (dysarthria and apraxia of speech)
result from neurological impairment in the areas of the brain
responsible for motor planning, motor programming,
neuromuscular control, and execution of speech; and they
account for 41% of all acquired communication disorders
(Yorkston, Beukelman, Strand, & Bell, 1999; Duffy, 2005).
Dysarthria can cause a reduction in speaking rate, abnormal
prosodic features, and significant intelligibility deficits
resulting in a reduced ability to communicate successfully
(Ansel & Kent, 1992; Kent, 1992; Duffy, 2005).
Apraxia of speech is commonly characterized by groping,
inconsistent articulation errors, especially in longer utterances,
and increased errors in repetition based tasks; therefore, the
apraxic speaker exhibits problems of speech initiation, speech
sequencing, speech selection, reduced rate of speech,
disturbances in articulation and rhythm, abnormal prosody,
and decreased intelligibility (Dworkin, 1991; Chapey, 1994;
McNeil, 1997; Yorkston, et al., 1999; Wambaugh & Nessler,
2004).
Treatment of motor speech disorders may consist of
behavioral, medical, and assistive treatment techniques.
(Duffy, 2005).
One behavioral technique to improve communication is
slowing speaking rate.
Duffy (2005) states, “Rate may be the most powerful single,
behaviorally modifiable variable for improving intelligibility”
(p. 479).
Purpose
Slowing speaking rate has been found to be an effective
therapy technique for both dysarthria and apraxia of speech
(Simmons, 1978; Yorkston and Beukelman, 1981; Yorkston et
al., 1999). One of the outcomes of slowing speaking rate is an
improvement in speech intelligibility (Southwood, 1987;
Wambaugh and Martinez, 2000); however, few studies have
documented the effectiveness of methods for the control of
speaking rate in individuals with motor speech disorders. The
purpose of this study is to evaluate a training program aimed
at slowing speaking rate for read sentences in an individual
with both dysarthria and apraxia of speech through the use of
visual, auditory, and verbal feedback.
METHODS
Participant
The participant in this investigation was a forty-nine-year-old
male who has developmental speech and language deficits (see
Table 1). He reported that though he had the communication
disorder since childhood, he received no speech remediation
services during the years of his formal education.
The participant was diagnosed with mild-moderate apraxia of
speech and dysarthria. The participant had not received
speech therapy for two years prior to this study.
Table 1: Assessment Results
Measure
Result
Apraxia Battery for Adults-2nd ed.
mild & moderate
(majority of ratings)
Ross Information Processing Assessment-2nd ed.
severe rating
immediate memory
recall of general information
spatial orientation
marked rating
recent memory
temporal orientation (remote memory)
moderate rating
temporal orientation (recent memory)
organization
problem solving and abstract reasoning
mild rating
auditory processing and retention
orientation to environment
Frenchay Dysarthric Assessment
most impaired areas
jaw, tongue, intelligibility
Western Aphasia Battery
Aphasia Quotient (100 possible)
86.6
language deficits
writing, reading, word fluency
Phonetic Intelligibility Test
word intelligibility score
69%
Experimental Design
The experimental design used in this study consisted of a
single-subject ABAB research design. The first A phase is the
baseline phase and was continued until speaking rate stability
was achieved. Stability was defined as average sentence
duration of the 18 stimulus sentences falling within +/-5% of
each other over three consecutive baseline sessions. The first
B phase consists of the treatment phase where the participant
was trained to reduce speaking rate. The second A phase
represents the withdrawal phase. During this phase the
participant did not receive treatment. Reinstatement of
treatment represents the second B phase and was completed in
the same way as the first treatment phase. Sentence duration
and speech intelligibility was acquired on a weekly basis
during the last three phases and every other day during the
first phase.
Choosing Target Speaking Rate
The speaking rate that maximized the participant’s
intelligibility was used as the target rate for this study. To find
this rate, the participant produced the 18 stimulus sentences
(each seven syllables in length) at his habitual rate and at 90%,
80%, 70%, 60%, and 50% of the habitual rate.
The participant was presented with a prerecorded auditory model of
each of the 18 sentences at a targeted sentence duration associated
with the targeted speaking rate (e.g., 90%). The intensity
waveform of each model was presented both auditorily and visually
to the participant through the use of the Real-Time Pitch program
within the Sona-Speech II, model 3650 program (KayPentax,
2006). In addition, the participant was trained to use the visual
feedback of his own sentence productions from the Real-Time
Pitch program to match the model production.
The investigator put two vertical lines on both the top and
bottom panels of the Real-Time Pitch screen indicating the
target duration range (i.e. mean plus and minus five percent
plus reaction time). The participant was asked to produce the
different target rates by slowing articulation time and not
increasing pause time. The participant produced each sentence
until one production fell within the target duration range. This
resulted in a total of 108 sentence productions (18 sentences X
6 speaking rates).
Three listeners listened to a digitized recording of each of the
18 sentences for a given speaking rate and orthographically
transcribed each sentence. The speaking rate judged as
having the highest intelligibility rating was 60% of the
participant’s habitual speaking rate.
Treatment
The treatment phase of this study focused strictly on slowing
rate of the nine training sentences to a target durational range
of 4.39-4.85 seconds. The target sentence duration range
represents +/- 5% of the average duration of the 60% target
speaking rate. This range was chosen based on a study by
Hyland and Weismer (1988).
The participant’s target duration range was changed from +/5% to +/- 7.5% of the participant’s habitual speaking rate
during week six of the first treatment phase. This was done
based on the observation of the experimenter that the
participant was consistently short of the smaller target range
and was unable to make progress.
For each sentence produced by the participant the
investigator first displayed and played one of her
prerecorded sentences in the upper panel of the computer
screen and noted how the end of the time history of her
sentence ended between the vertical lines indicating target
duration range. The participant was directed to the lower
screen containing the same set of vertical lines. When the
participant was prepared, he was asked, “Are you ready”
by the instructor, he replied “Yes” and the instructor then
said, “Begin” and began recording at that time while the
participant then produced the same sentence. The sentence
was recorded and displayed as an intensity time history
trace in the lower panel of the computer screen. This was
repeated three times for each sentence regardless of
accuracy.
The participant received verbal, auditory, and visual feedback
after his production. Verbal feedback consisted of knowledge
of performance and knowledge of results.
Treatment sessions consisted of distributed practice and
random practice of the training sentences within and across
treatment sessions, with the focus on slowing rate by
increasing articulation time and not by inserting pauses.
Treatment continued until the participant reached the target
speaking rate of 60% of his habitual rate with 80% accuracy
over three consecutive treatment sessions. After reaching the
criterion, the withdrawal phase began.
The Second B Phase was conducted in the same way as the
First B Phase. The last three phases of the study continued for
seven weeks.
One time each week, throughout the treatment phase,
withdrawal of treatment phases, and reinstatement of treatment
phase, both the trained and untrained sentences were recorded
in a single walled sound booth. One time a week, on random
days, the participant was tape recorded using the Tascam DAT
tape recorder and Crown CM311A head mounted microphone
while spontaneously producing the 9 trained sentences and the
9 untrained sentences to evaluate generalization.
Each tape recorded sentence was digitized at 44.1 kHz via the
TF32 program (Milenkovic, 2002) and displayed on the screen
in the form of a sound pressure waveform. Cursors were
placed at the beginning and end of the sentence for
measurement of sentence duration.
In order to collect weekly intelligibility measures, the digitized
sentences were normalized to -3 dB and presented to three
listeners through a customized software program developed in
Revolution 2.8.1 (www.runrev.com). The PC-based program
used Quick Time to play .wav files through the computer’s
sound card. The listeners had the opportunity to listen to each
sentence twice (Yorkston & Beukelman, 1981). Each listener
listened to the sentences through loudspeakers at a self-chosen
most comfortable listening level. The listeners
orthographically transcribed the sentences on a keyboard. The
investigator calculated the percent correct (total words
correctly identified) for each of the three listener’s
transcription for the trained and untrained sentences and
calculated an average percent correct across the three listeners.
The intelligibility data will not be presented in this poster.
RESULTS
Accuracy Results Within the Treatment Program
Accuracy data was collected during the treatment phases (Refer
to Figure 1).
The first treatment phase was terminated after the participant
achieved 80% accuracy of the target duration/speaking rate (60%
of his habitual) for three consecutive sessions. It took seven
weeks to meet exit criterion during the first treatment phase.
The withdrawal phase and second treatment phase also
continued for seven weeks in order to equalize the effects of
extraneous variables (McReynolds and Kearns, 1983).
During the second treatment phase the participant achieved
criterion by the 4th session and maintained an average of 93%
accuracy after criterion was achieved.
Duration Results of Trained Sentences
Results indicate the participant reached a stable average
sentence duration/speaking rate of 2844 ms during baseline
measurements (final 3 data collection points) of the trained
sentences (Refer to Figure 2).
Sentence duration was variable during the first treatment
phase for trained sentences. It ranged from 2698-3967 ms
The participant was not successful in slowing sentence
production to his goal of 60% of his habitual speaking rate.
The participant, however, was able to slow speaking rate to a
maximum of 70% of his habitual speaking rate.
Results indicate the participant was able to slow his habitual
speaking rate (increase sentence duration) in 6 out of seven
sessions during the first treatment phase.
Withdrawal data indicates the participant produced a stable
sentence duration ranging from 2962-3117 ms compared to
range of 2698-3967 ms for the first treatment phase,
indicating an increase in speaking rate.
The data collected during the second treatment phase was
also variable. The client was able to alter speaking rate;
however, he was not successful in achieving his goal of 60%
of habitual speaking rate. Average sentence duration in the
second treatment phase ranged from 2967-3975 ms
indicating an increase in sentence duration relative to the
withdrawal phase. Results indicate the participant was able
to slow his speaking rate relative to his average habitual
speaking rate for the baseline phase in all 7 of the data
collection sessions during the second treatment phase.
Duration Results of Untrained Sentences
Duration results of the untrained sentences were similar to the
results of the trained sentences (Refer to Figure 3).
The participant’s average habitual speaking rate for the untrained
sentences was determined to be 2620 ms during baseline
measurements.
The data collected during the first treatment phase indicated that
the participant was able to slow his speech, but unable to reach a
slowed rate of 60% of his habitual speaking rate. Sentence
duration in the first treatment phase was variable and ranged from
2754-3829 ms. The participant was only able to reach a maximum
slowed speaking of 70% of his habitual speaking rate relative to
average habitual speaking rate for the baseline phase. The
participant slowed his speaking rate (increased sentence duration)
in all 7 data collection sessions in the first treatment phase.
Withdrawal data indicates the participant produced a stable
sentence duration range of 2908-3136 ms compared to range
of 2754-3829 ms for the first treatment phase, indicating an
increase in speaking rate.
The data collected during the second treatment phase was also
variable. The client was able to alter speaking rate; however,
he was not successful in achieving his goal of 60% of habitual
speaking rate. Average sentence duration in the second
treatment phase ranged from 2698-3843 ms, indicating an
increase in sentence duration relative to the withdrawal phase.
The participant was able to slow his speaking rate relative to
average habitual speaking rate for the baseline phase, and
increase sentence duration in all 7 of the data collection
sessions in the second treatment phase.
CONCLUSIONS
The participant was able to alter his speaking rate and produce
the trained sentences at 60% of his habitual speaking rate with
80% accuracy during therapy, but was unable to transfer the
new speaking rate to data collection outside of the therapy
room. That is, the participant’s performance during data
collection did not reflect performance during treatment.
However, on average the participant did slow his habitual
speaking rate for both treatment phases relative to the baseline
and withdrawal phase.
Speakers with AOS do not consistently adjust speaking rate
for sentences when instructed to speak at given rates (Robin,
Bean and Folkins, 1989). This was true for the present
speaker and was the reason for expanding the target range.
Perhaps the client would have produced a slower speaking rate
if he was told specifically during data collection to reduce his
speech to exactly what he had practiced during the treatment
session. This was attempted after the treatment program had
concluded and verbal instruction by itself was found to be
unsuccessful.
Another possibility for lack of generalization of the new
speaking rate outside of he therapy room may be due to the
participant’s deficits in the area of memory as indicated in the
results of the Ross Information Processing Assessment (See
Table 1).
The participant’s ability to generalize was observed to be
dependent on the time of data collection within a session (i.e.,
beginning or end of session). If data was collected at the
beginning of the therapy session, speaking rate was faster than
if it was collected at the end of the therapy session. These
findings support the influence of the participant’s memory
deficits on his ability to generalize.
A final reason for the lack of generalization may be due to the
fact that the generalization task involved removal of all cues
(i.e., visual, auditory and verbal). Articulatory methods for
treatment of AOS focus on gradual removal of cueing
(Yorkston et al. 1999). A more programmatic decrease in
cueing may have lead to better generalization of rate.
Future Research
Replication of this study should be completed with different
participants exhibiting motor speech disorders.
The evaluation of the effectiveness of different feedback
modes (i.e., visual, verbal, and auditory feedback) on
acquisition and generalization of a slowed speaking rate
should be documented.
Investigation of the interaction between different modes of
feedback in the training of a slowed speaking rate along with
participant characteristics should be addressed.
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