Hargrove et al. (1989a)


Single Subject Designs


SOURCE:  Hargrove, P. M., Dauer, K. E., & Montelibano, M. (1989a). Reducing vowel and final consonant prolongations in twin brothers. Child Language Teaching and Therapy, 5, 49-63.


DATE:  7.05.13


TAKE AWAY:  These 2 case studies provide initial, limited support for procedures for reducing the prolongation of vowels and consonants in preschool children. The authors make the case that the prolongations were prosodic rather than segmental in nature.


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?  Case Studies – Description with Pre and Post Test Results  

b.  What was the level of support associated with the type of evidence? 

Level =  D+                                                      


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?  2

b.  The following characteristics were described:

•  age:  4 years  (twins)

•  gender:  m

•  expressive language: 4 years; 4 months  and 7 years [Preschool Language Scale (PLS) at 4 years, 2 months]  

•  receptive language:  4 years; 4 months  and  4 years; 6 months (PLS at 4 years, 2 months)  

c.  Were the communication problems adequately described?  Yes

•  The disorder types were atypical expressive phonology (vowels) and prosody*

•  Other aspects of communication that were described

–  production of consonants:  WNL accuracy but Ps tended to prolong final consonants

–  production of vowels:  multiple substitutions (including nondialectial diphthongs and triphthongs) and frequent prolongations (generally with a wide falling pitch or pitch perturbation)

–  relative frequency of prolongations in spontaneous speech: 0.407 and 0.401 ratio of prolongations to word tokens (# of prolongations/ # of word tokens)

–  other prosodic concerns:  pitch modulation on prolongations, excessive and equal stress, few rising intonations, and limited affect.


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? No , these were case studies.

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?  No

e.  Were different treatment counterbalanced or randomized?  Not Applicable 


7.  Were the outcomes measure appropriate and meaningful?  Yes

a.  The outcomes were


  OUTCOME #1:  To decrease the rate of vowel and consonant prolongations in selected single words

  OUTCOME #2:  To decrease the rate of vowel and consonant prolongations in spontaneous speech

NONINVESTIGATED TARGETS (These are included to inform readers of overall intervention context; results were not reported.)

OUTCOME #3:  To increase the number of unstressed syllable and unstressed words

  OUTCOME #4:  To increase the frequency of appropriate rising terminal contours

  OUTCOME #5:  To increase the number of different types of pitch changes

b.  All the outcomes were subjective.

c.  None of the outcomes were objective.

d.  None of  the outcome measures were associated with reliability data.


8.  Results:

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

b.  The overall quality of improvement was

OUTCOME #1:  To decrease the rate of vowel and consonant prolongations in selected single words  Strong for both Ps

OUTCOME #2:  To decrease the rate of vowel and consonant prolongations in spontaneous speech  Strong for both Ps

9.  Description of baseline:

a.  Were baseline data provided?  No


10.  What was the magnitude of the treatment effect?  NA


11.  Was information about treatment fidelity adequate?  Not Provided


12.  Were maintenance data reported?   No


13.  Were generalization data reported? Yes.  Outcome #2 involved measuring the length of words not taught in treatment sessions.






PURPOSE:  To document progress associated with an intervention designed to reduce the production of  prolonged vowels and final consonants.

POPULATION:  impaired phonology (vowels) and prosody [preschoolers]





DOSAGE:  25 minutes, 2 to 3 times a week, for 7 months, months 1-3 individual sessions, remaining sessions were joint sessions with both twins. Outcomes #3-5 were also treated during the sessions.




STIMULI:  auditory, visual





TECHNIQUES:  imitation, modeling, contingent reinforcement, verbal feedback, conversation, elicited speech, games, auditory cues, visual cues.  (Descriptions and examples of several of these procedures are provided in the article.)


–  Steps 1a and 1b – 95% accuracy

–  Steps 1c through 1i — 100% accuracy

–  Steps 2a and 2b – 80% accuracy

TARGET:  no prolonged consonants or vowels


NOTE:  If P does not perform the task described in the Steps, C assists P in achieving the production using modeling, verbal feedback, auditory cues, visual cues at C’s discretion (i.e., loose training).  C provides multiple different stimuli for each of the steps.

1a.  C directs P to imitate a vowel in isolation,

1b.  C directs P to imitate a nonsense CV syllable (e.g., /gi/),

1c.  C displays a picture of a CV word (e.g., bow) and requests P to name it.  For example, C displays the number 2 and says: “What is this?”

1d.  C directs P to imitate CVC real (e.g., top) and nonsense (e.g., zub) words with stops in the final position,

1e.  C displays pictures of CVC words (e.g., gate) with stops in the final positions and asks P to name it.

1f.  C directs P to imitate CVC real (e.g., man) words with fricatives, nasals, affricatives, or semivowels in the final position,

1g.  C displays pictures of CVC words (e.g., ball) with fricatives, nasals, affricatives, or semivowels in the final positions and asks P to name them.

1h.  C elicits spontaneous productions of disyllable (e.g., candy) words by showing P the picture an asking P to name it.

1i.  C shows P a picture of a multisyllabic  (e.g., strawberry) word and asks P to name it.

2a.  C displays a pictured action and requests P to explain what is happening (e.g., The girl is standing on the ladder.)

2b.  C and P play a game (e.g., Concentration) in which turns are taken when one of them  describes an action picture (e.g., The boy is holding a cookie).

*  The rationale for designating a combined segmental and nonsegmental  (prosody) phonological problem was

1.  The overall rate of vowel errors increased only slightly for one P and moderately for the other.

2.  The nature of vowel substitutions did change. The ratio of diphthongs and triphthongs substitutions for single vowels decreased markedly (from 0.79 to 0.21 and from 0.93 to 0.07).

3.  Ps prolonged both vowels and consonants although consonants were age appropriate.

4.  There was evidence of other prosodic problems:  pitch modulation on prolongations, excessive and equal stress, few rising intonations, and limited affect.


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