Wambaugh et al. (2012)


Single Subject Designs


Note: The summary can be viewed by scrolling about two-thirds of the way down on this page.


SOURCE: Wambaugh, J., Nessler, C., Cameron, R., & Mauszycki, S. C. (2012). Acquired apraxia of speech: The effects of repeated practice and rate/rhythm control treatments on sound production accuracy. American Journal of Speech-Language Pathology, 21, S5- S27.




DATE: April 7, 2014


ASSIGNED OVERALL GRADE:  A- (The highest possible grade is A-.)


TAKE AWAY: The focus of these single subject experimental design studies was primarily on repeated practice with investigators employing and analyzing rate/rhythm as a strategy to increase effectiveness after the primary intervention. Rate/rhythm intervention was successful in increasing the production of speech sound accuracy following repeated practice intervention.


1. What was the focus of the research? Clinical Research



2. What type of evidence was identified?                              

a. What type of single subject design was used? Single Subject Experimental Design with Specific Client: Combined design—ABCA, multiple probe across behaviors, multiple baseline across Ps

b. What was the level of support associated with the type of evidence? Level = A-      



3. Was phase of treatment concealed?                                 

a. from participants? No

b. from clinicians? No

c. from data analyzers? No



4. Were the participants adequately described?  Yes

a. How many participants were involved in the study? 10


– The following characteristics/variables were controlled: diagnosis of chronic apraxia of speech with nonfluent, agrammatic aphasia (Broca’s aphasia)

– The following characteristics were described:

• age: 33-60 years

• gender: 7m, 3f

• cognitive skills: WNL                 

• native language:   all English native speakers

• concurrent speech-language therapy: No

• psychosocial status: negative history for substance abuse, psychological disorders       

• neurological status: negative history with the exception of the stroke

• etiology: single stroke; all CVAs

• site of lesion: 9 Ps left hemisphere, 1 P right hemisphere; 8 middle cerebral artery, 1 anterior cerebral artery, 1 basal ganglia

• years post onset: 1 to 19 years

• handedness (premorbid): 6 right, 3 left, 1 ambidextrous

• years of education: 12 to 21 years


c. Were the communication problems adequately described? Yes

• List the disorder type(s): of chronic apraxia of speech with nonfluent, agrammatic aphasia (Broca’s aphasia)

• List other aspects of communication that were described:

— hearing: WNL

— intelligibility: 68%- 96%

— overall PICA: 40- 71

— WAB aphasia quotient: 24.8 – 78



5. Was membership in treatment maintained throughout the study? Yes

a. If there was more than one participant, did at least 80% of the participants remain in the study? Yes

b. Were any data removed from the study? No



6. Did the design include appropriate controls? Yes

a. Were baseline/preintervention data collected on all behaviors? Yes

b. Did probes/intervention data include untrained data? Yes

c. Did probes/intervention data include trained data? Yes

d. Was the data collection continuous? Yes. There were 5 probe lists, some were continually measures, other were periodically measured.

e. Were different treatment counterbalanced or randomized? No, by design the repeated practice procedure was administered first, then the rate/rhythm procedure was administered.



7. Were the outcomes measure appropriate and meaningful? Yes

a. The outcomes were

  • OUTCOME #1: Improved production of P’s designated speech sounds in words (or for one P, sentences) during an imitation task.

• OUTCOME #2: Improved percentage of correct consonants (PCC) in words (or for one P, sentences) during an imitation task.

b. Both of the outcomes that are subjective.

c.  None of the outcomes were objective.

d. The data supporting reliability of outcomes is

• A measure of combined reliability across all lists and Ps that ranged from 83% to 97%; the average was 91%.



8. Results:

a. Did the target behavior improve when it was treated? Yes

b. Only data for OUTCOME #1 were statistically analyzes.

• Improvement for Repeated Practice Procedures:

– 8 of the 10 Ps improved, although the degree of improvement varied (Overall Quality—Moderately strong)

• Improvement for Rate/Rhythm Procedures (administered only when Ps did not achieve maximal gains from Repeated Practice Procedures):

– Limited gains were achieved for 6 of the 8 Ps who were treated with Rate/Rhythm Procedures.


9. Description of baseline:

a. Were baseline data provided? Yes

• OUTCOME #1: Improved production of P’s designated speech sounds in words (or for one P, sentences) during an imitation task—Because of the nature of the design, the number of baseline data varied across the 10 P but there was a minimum of 5 baseline data points for each P.

b. Was baseline low and stable?

•   OUTCOME #1: Improved production of P’s designated speech sounds in words (or for one P, sentences) during an imitation task—Generally the baseline was low and stable.

c. What was the percentage of nonoverlapping data (PND)? Not provided



10. What was the magnitude of the treatment effect.”

• OUTCOME #1: Improved production of P’s designated speech sounds in words (or for one P, sentences) during an imitation task.

– magnitude of effect: varied based on procedure, probe list, and P. Of those who made progress (8/10), d ranged from 0.78 – 16.47.

– measure calculated: d

– interpretation:  Strong improvement.



11. Was information about treatment fidelity adequate? Not Provided



12. Were maintenance data reported? Yes. For the 8 Ps who benefitted from the interventions, there was a strong tendency to maintain and even improve performance when assessed 4 and 8 weeks after the termination of therapy.



13. Were generalization data reported?Yes. Seven of the 8 Ps who improved evidenced generalization to untreated probe lists.







(summary is only concerned with the rate/rhythm intervention)


PURPOSE: The primary purpose was to investigate the effectiveness of repeated practice on the accuracy of production of speech sounds. The secondary purpose was to determine if the gains from repeated practice could be enhanced when repeated practice is followed by rate/rhythm intervention. (That is, repeated practice and rate/rhythm interventions were not compared.)


POPULATION: apraxia of speech and Broca’s aphasia




ELEMENTS OF PROSODY USED AS INTERVENTION (part of independent variable: rate, rhythm




DOSAGE: 3 times a week, sessions (probes plus interventions) lasted 1.25 to 1.5 hours, number of sessions varied from about 23-45 sessions for combined treatment and approximately 9-20 sessions for rate/rhythm only




STIMULI: auditory, motor/kinesthetic




1. C constructs sentence or word lists for the P taking into considerations P’s error patterns and the optimal overall length of stimuli (single words or sentences) and syllable patterns.

2. C models a targeted word or sentence for the P accompanied by hand tapping guided by the beat of a metronome. (The metronome was set a 50% of P’s customary rate of syllable production.)

3. C instructs P to repeat the target 5 times in succession.

4. C provides only general feedback about the acceptability of speech sound production, even if P requests for more specific information.

5. The procedure continues through each of the items on the target list.

6. C presents the target lists 3 times during the session.




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