There’s a practice that has quietly become standard in speech pathology, one so widespread that many of us have never stopped to question it. I know I didn’t — not for a long time. It goes like this: a child says “wabbit” for “rabbit,” and we call it gliding, they say “bacuum” for “vacuum,” and we call it stopping, “fum” for “thumb” becomes fricative simplification. Every speech error gets a phonological process label.
This approach is taught at university. It’s modelled by supervisors. It’s prevalent in most speech pathology reports. For years, I followed it too — because when everyone around you is doing something the same way, it’s easy to assume it must be the right way. It took me a long time to question it, and even longer to say, clearly and confidently: the research doesn’t support it. I’m saying that now.
Here’s why it matters.
Articulation vs. Phonological Processes: The Core Distinction
A useful starting point is to think of articulation as “in the mouth” and phonological processes as “in the brain.” Articulation is motor-based; phonology is linguistic and rule-based.
It’s worth pausing here to acknowledge that new research is complicating this dichotomy — and rightly so. Emerging evidence suggests that the majority of speech sound errors involve both motor and phonological components, rather than falling neatly into one category or the other. This is something many clinicians have intuitively felt for a long time, and it’s exciting to see the science catch up.
That said, understanding the broad differences between these two types of errors remains clinically important.
Articulation errors:
- Are phonetic (sound-specific)
- Typically affect a small number of sounds, usually later-developing ones
- Stem from the child learning an incorrect motor pattern
Phonological delays (where typical phonological processes persist beyond the expected age):
- Are phonemic and they follow rule-based patterns
- Affect entire syllable shapes (e.g., cluster reduction, final consonant deletion) or entire classes of sounds (e.g., stopping, fronting, gliding)
- Reflect a child using simplification strategies longer than expected
This distinction is the crux of the issue.
Why Labelling Single-Sound Errors as Phonological Processes Is Problematic
Phonological processes, by definition, involve patterns across classes of sounds. Stopping, for example, affects fricatives as a group. Fronting affects velar sounds as a group. These are systematic, rule-governed simplifications.
But what happens when only one sound is affected?
Take the example of a child who substitutes /v/ with /b/, while producing all other fricatives correctly. This is not “stopping.” Stopping would require the pattern to affect the broader class of fricatives — not just one. Similarly, a child who says /f/ for voiceless /th/ but produces all other fricatives accurately is not demonstrating “fricative simplification.” They simply haven’t yet acquired the /th/ sound and are substituting it with one they can produce.
Labelling these individual sound errors with a phonological process name is inaccurate. It implies a broader, systematic pattern that isn’t there.
So What Should We Call Them?
Simple: substitutions.
- /v/ → /b/ (with other fricatives intact) = a /b/ for /v/ substitution
- /r/ → /w/ (with /l/ produced correctly) = a /w/ for /r/ substitution
- /th/ → /f/ (with other fricatives intact) = a /f/ for voiceless /th/ substitution
This language is precise and clinically meaningful. It accurately describes what the child is doing without overstating the scope of the error.
A More Accurate Framework
At our practice, we distinguish between two categories:
- Articulation errors — labelled as substitutions (X for X)
- Phonological processes — labelled according to the process affecting a class of sounds
Importantly, this distinction doesn’t mean we treat them in completely separate silos. In practice, effective therapy for both types of errors tends to integrate articulation strategies (teaching correct motor production) with phonological approaches, such as minimal pairs, that help children understand how sounds change the meaning of words.
The goal is accuracy in both our thinking and our language. When we call something a phonological process, it should be a phonological process. And when a child has a single-sound substitution, we should describe it as exactly that.
A Note on Challenging the Norm
If you’re reading this and feeling a little uneasy — because this is what you were taught, or what you’ve been doing for years — I understand. I was there too. The fact that a practice is widespread doesn’t make it correct and recognising that takes intellectual honesty.
This isn’t about blame. It’s about doing better for our clients, and for the rigour of our profession.
The research is there. The distinction is clear. And our assessment reports, clinical reasoning, and treatment planning will all be stronger for getting it right.
