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Correctly Matching Speech Sound Disorders to Appropriate Therapy

I want to share a turning point for me for how I successfully treat kids who are hard to understand because of their speech sound disorders. I think that my speech therapy outcomes were pretty average when I began speech therapy. Some kids totally soared and got dismissed easily. A small handful languished on my caseload even as I made every attempt to help them or attended new conferences on speech sound disorders. I was never quite sure if I was making a difference or if they were just getting older.

Then I was introduced to a behavioral research model that suggested that:

  1. “Unintelligible” speech needs to be more clearly defined
  2. There are many different classes of “unintelligible” speech
  3. Each different class may require a different style of intervention

What it suggested to me is that I was kind of all over the map with my therapy approach. When I better understood how a child was unintelligible, I was better able to clean up their speech. It all started with the first piece of data:

speech sound disorder types
Broomfield and Dodd 2004

What Broomfield and Dodd (2004) were suggesting was that most (87%) speech sound disorders were phonological in nature. I don’t know about you, but I was doing articulation therapy with more than 13% of my caseload.

Secondly, that there is more than one kind of phonological error.

Thirdly, that some of these phonology types made a child more unintelligible.

And fourthly, they didn’t all benefit from the same type of intervention.

Does that blow your hair back? I had a choice. Be depressed and embarrassed about the level of therapy I was giving or ecstatic to have a way to improve. To be honest, I was both.

When these researchers took these categories and started differentiating treatment depending on the subgroup, they were finding gains in treatment in a child’s progress. So let’s go over these and then I am going to share a chart and infographic to help you determine which of your students fall into each category.

Here are the five subgroups. Within phonology, we have delayed phonological impairments, consistent deviant phonology, inconsistent deviant, and then articulation. They have an “other” or miscellaneous category in this research which includes fluency, structural anomalies, or anything really specific.

speech sound disorder research

It’s also important for us to keep in mind that there are some children that can overlap in categories. Yes we can have a student who has difficult producing specific sounds and employing sound rules. They would overlap with the articulation category and phonological groups.

Delayed Phonological Skills

Definition: Phonological system similar to younger, typically developing children. Most phonemes can be articulated; however, discrepancies exists between phonological processes observed and a child’s chronological age.

What we see:

  • Multiple misarticulations
  • Errors can be classified by patterns
  • See typical patterns that persist (e.g., stopping, cluster reduction, liquid simplification)

Phonological delays are pretty familiar to all of us. We have heard them from really young children and a child needs to be treated if the pattern is still around when they are older. Intervention for this group includes pattern-based approaches such as:

  • Distinctive Feature approach
  • Phonologically-based intervention
    • Cycles
    • Phonological contrast therapy (Crosbie et al., 2005)
      • e.g., minimal pairs, maximal oppositions, empty set, multiple oppositions
    • Phonological Contrast 
      • Target:  Stopping sun—bun,  shin—pin, shoe—two

Consistent Deviant Phonological Disorder

Definition: Systemic use of deviant phonological rules (i.e., error patterns that are atypical of normal phonological development). e.g., deleting all syllable-initial consonants

What we see:

  • Less intelligible
  • Sound production may be age appropriate (Difficulty producing sounds in certain contexts)
  • Errors that are consistent patterns, but SHOULD NOT be seen by any child, at any age. E.g, deleting all syllable-initial consonants.

What makes a phonological process consistent and deviant is that a child produces a pattern consistently and it never should have been around, even at a young age. Here are the processes we should see at a young age versus the ones that we shouldn’t:

Delayed or Deviant Phonological Patterns?

Delayed Phonological SkillsConsistent Deviant Phonological Skills
Cluster ReductionDeaffrication
Liquid SimplificationInitial Consonant Deletion
Velar FrontingSpirantization
Weak Syllable DeletionDenasalization
Final Consonant DeletionPalatalization
Palatal FrontingMetathesis
 Spirant Deletion

The good news is that this sound class is treated the same way as phonology. The bad news is that these processes make a child highly unintelligible. For example, a child who deletes the final consonant (do_, ca_, bir_) is way more intelligible than a child who deletes the initial consonant (_og, _at, _ird).

Inconsistent Deviant Phonological Disorder (IDPD)

Definition: Variable productions of the same words or phonological features in the same contexts and across contexts.


  • Say “butterfly”
  • “Chutterdy”
  • Again, say “butterfly”
  • “sunnerny”

The IDPD speech sound disorder group requires very different treatment. These students can name sounds and sing the alphabet but are extremely unintelligible in connected speech. Moreover, when we work on producing sounds, they can say something different each time we ask them to. The goal of intervention is CONSISTENCY at the single word level. 

Intervention Example:  Important Vocabulary Approach

  • List of 50 target words chosen for child
  • 10 words targeted during the week
  • Consistent words then removed from list, and new set of 10 words chosen randomly for practice
  • Generalization monitored through periodic probe of untreated words

This therapy approach resulted in greater change in children with inconsistent speech disorder compared to more traditional approaches (Crosbie et al., 2005)


Definition: An inability to produce a perceptually acceptable version of particular phonemes, either in isolation or in any phonetic context.

What we see:

  • “/r/, /s/, and /l/ kids”—errors with a particular sound
  • Can be highly intelligible

This requires “Traditional Artic”/motor-based approaches. Shoot for at least 100 prompts of a sound! Distributed practice over time is more effective for retention than massed practice (Willingham, 2002).

  • Teach motor behaviors associated with the production of a particular speech sound
    • Van Riper approach
    • McDonald’s sensory-motor approach (use of facilitative contexts)
    • Multiple Phoneme approach

Miscellaneous Speech Sound Disorders

Definition: Low intelligibility attributed to physiological factors such as hearing impairment or craneo-facial anomalies.

What we see:

  • Extremely low intelligibility
  • External services needed
  • Compensation strategies needed to reduce the impact of the physiological factor.

This requires very specific therapy depending on the disorder at hand.  Check out our courses on VPI and Cleft Lip which we put together after our trips with cleft palate surgical teams to Mexico and Central America and also our course on hearing impairment and cochlear implants.

How Do I Tell the Difference Between the Classes Of Speech Sound Disorders?

We built the following decision tree and therapy chart to help you figure out what you should be working on. Let me tell you how it works but I also want to tell you that I also made a CEU course where you can see video examples of each of the disorders and before-and-after therapy examples so you know exactly what to do.

Start on the bottom of the tree. You need to identify if errors are due to a pattern or are sound-specific. For the patterns you need to determine if they are consistent errors or not. For the sound errors, you need to figure out if they are due to a structural anomaly or not.

Once you have your answer, go over to the chart and see which therapeutic processes have been shown to be effective for each disorder. That’s it! 

Bilinguistics speech sound disorder decision tree

Bilinguistics speech sound disorder chart

Written by: Scott Prath

6 Comments on “Correctly Matching Speech Sound Disorders to Appropriate Therapy”

  1. January 26, 2023 at 7:46 pm #

    This is a great overview, as far as it goes, but you did not mention any motor speech sounds, such as dysarthria or childhood apraxia of speech. It is important for SLPs to be able to differentially diagnose phonological vs. motor-based speech sound disorders.

    • January 31, 2023 at 3:27 pm #

      Totally true Patricia. I should have further described what “Misc” meant. Vanessa made a similar observation and there are a ton of other influences on intelligibility that this tree can’t cover. You mentioned motor with a dysarthria/apraxia division. And there is VPI/cleft/fluency/hearing and you could even add degenerative disease. Others here, please chime in with what we haven’t mentioned yet. I attempted to cleanly delineate between phonology and articulation. This research got me excited about that. But you are hinting at how much further it could be taken. I like that.

  2. January 27, 2023 at 2:55 am #

    This is a really useful article; thank you so much for the graphs and visuals as well. I want to print them for my office! I would add that treatment of motor-speech disorders, such as apraxia an dysarthria, follows (or needs to follow, in order to be effective) a very different path than articulation disorders. In motor speech disorders, not only articulators are affected, but also resonation, phonation and respiration– all four movement subsystems. SLPs may find themselves needing to help treat vowels, prosody, oronasal distinctions, and even transitions that go into creating a CV syllable. We typically wouldn’t observe these needs in an articulation client practicing /l/ or /r/. Again, this article is extremely helpful as I have found myself in a similar situation you describe– often not totally clear about which approach to use for which type of speech sound disorder. And motor speech disorders, as an additional category, can be among the most challenging to remediate.

    • January 31, 2023 at 3:20 pm #

      Thank you for your comment Vanessa. In the original research the category “Misc.” covered hearing-loss influenced speech, stuttering, etc. I love that they acknowledged that there are other cases and this is a phonology-artic paradigm. What if someone made a tree with all of those though? That would be pretty cool. More like a jungle when you add VPI Cleft, what you mentioned – “motor speech disorders, not only articulators are affected, but also resonation, phonation and respiration”… But I like the idea of seeing a single visual that describes “intelligibility.” Imagine an electronic version that hopped you through and then gave you goals and proper therapy ideas?

  3. March 18, 2023 at 9:34 am #

    Great article- the best way I’ve seen speech sounds disordered described and differentiated. Thank you!
    Are your visuals for the Decision Tree and Definition chart available somewhere on your site? I would love to have those resources to print out. Thank you in advance!

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