"Tat" for "cat." "Wabbit" for "rabbit." "Poon" for "spoon." These are the speech errors most parents (and most GPs) recognise — the familiar, developmental, often-charming mispronunciations that children usually grow out of. We cover those in detail in our companion article on delayed speech sound patterns.
This article is about a different group of errors entirely — the ones that often get missed precisely because they don't look like what most people expect a "speech delay" to look like. Atypical speech sound errors are patterns that aren't part of normal speech development at all. A child might replace front sounds with back ones, drop the beginnings of words, or use a single "favourite" sound in place of many others. These patterns don't appear on any developmental timeline, and, crucially, they usually won't resolve on their own.
Understanding them can make a real difference to getting the right kind of help, at the right time.
Delayed vs. Atypical: What's the Difference?
To make sense of atypical errors, it helps to understand the difference between delayed and atypical speech sound patterns.
Delayed patterns are ones that all children use at some stage but that should resolve by a certain age. For example, saying "tup" for "cup" (fronting) is completely normal in a two-year-old, but we'd expect it to have resolved by around age 3 to 4. If a child is still doing it at age 5 or 6, that's a delay — they're on the typical path, just behind schedule.
Atypical patterns are different. These are sound substitutions or patterns that are not part of normal speech development. They don't appear on the typical developmental timeline, and they're not something most children do on their way to mature speech. Because of this, they usually don't resolve without targeted intervention.
This distinction comes from the work of Professor Barbara Dodd, whose classification system is widely used in Australian speech pathology. Dodd's model sorts speech sound difficulties into four subgroups (articulation, phonological delay, consistent atypical, and inconsistent) — and each one needs a different approach to therapy. For the full four-category framework laid out as a table, see Understanding Disordered Speech Sound Production. In this article, we're zooming in on the consistent atypical group.
What Do Atypical Speech Sound Patterns Look Like?
Here are some of the most common atypical patterns we see:
Backing
In typical development, young children often replace back sounds (like k and g) with front sounds (like t and d). This is called fronting, and it's a normal, expected pattern.
Backing is the opposite: a child replaces front sounds with back sounds. For example:
- "tea" becomes "kea"
- "dog" becomes "gog"
- "nose" becomes "ngose"
Because backing goes against the typical developmental direction, it's considered atypical and is a pattern that speech pathologists pay close attention to.
Initial Consonant Deletion
Most children go through a phase of leaving off the final consonant in words (e.g., "ca" for "cat") — this is a typical pattern that usually resolves by age 3.
Initial consonant deletion — leaving off the first sound in a word — is atypical. For example:
- "ball" becomes "all"
- "dog" becomes "og"
- "cup" becomes "up"
This pattern can make a child very difficult to understand because the beginnings of words carry a lot of meaning, and losing them changes or obscures many words.
Glottal Replacement
In this pattern, a child replaces consonant sounds with a glottal stop — a brief catch in the throat, like the sound in the middle of "uh-oh." For example, a child might say "bo-le" for "bottle" or "ki-en" for "kitten," replacing certain consonants with this throat sound.
Glottal replacement is not part of typical Australian English speech development and is considered an atypical pattern.
Sound Preference / Favourite Sound Substitution
Some children develop a "favourite" sound that they use to replace many different consonants. For example, a child might use d for almost every consonant: "dog" becomes "dog" (correct by coincidence), but "cat" becomes "dat," "sun" becomes "dun," "fish" becomes "dish," and so on.
When one sound is systematically substituted for a wide range of other sounds, it's considered atypical and can significantly affect how well others understand the child.
Other Atypical Patterns
Other less common but still noteworthy atypical patterns include:
- Adding sounds to words that shouldn't be there
- Unusual vowel changes that don't follow typical patterns
- Migrating sounds — moving a sound from one position in a word to another
Why Do Atypical Patterns Matter?
There are a few key reasons why identifying atypical speech sound patterns is so important:
They Don't Typically Resolve on Their Own
This is the biggest reason. Delayed patterns — the typical ones — often do resolve with time, even without therapy (though therapy can speed things up significantly). Atypical patterns, on the other hand, are much less likely to self-correct. Research consistently shows that children with atypical speech sound errors need targeted intervention to make progress (Dodd, 2014; Broomfield & Dodd, 2004).
Waiting to see if your child "grows out of it" is less appropriate when the patterns they're using are atypical. The sooner these patterns are identified and addressed, the better the outcomes. In my experience, atypical patterns are also the ones most likely to have been quietly flying under the radar — often because the child sounds "just a bit hard to follow" rather than obviously delayed.
They Can Significantly Affect Intelligibility
Because atypical patterns don't follow the rules that listeners subconsciously expect, they can make a child much harder to understand. A listener might be able to mentally "decode" a child who says "tat" for "cat" (because fronting is a familiar pattern), but backing, initial consonant deletion, or glottal replacement can be much harder to interpret.
They Require a Different Therapy Approach
This is where Dodd's classification system is so valuable. A child with delayed patterns benefits from approaches like minimal pairs therapy, which draws attention to the contrast between the error pattern and the target. A child with consistent atypical errors may need a different approach — such as core vocabulary therapy — because the underlying issue is different (Crosbie et al., 2005).
Getting the right diagnosis leads to the right therapy, which leads to better outcomes. That's why a thorough assessment is so important.
How Are Atypical Errors Identified?
A speech pathologist identifies atypical errors through a comprehensive speech sound assessment. This involves:
- Collecting a detailed sample of your child's speech sounds across many different words
- Analysing the patterns they're using — which are typical (just delayed) and which are atypical
- Assessing consistency — whether your child produces the same word the same way each time, or differently each time
- Considering the overall profile using a framework like Dodd's classification model
This kind of analysis goes beyond simply listing which sounds a child can and can't produce. It's about understanding the system behind the errors, so we can choose the most effective intervention.
Don't forget the ears. Unusual error patterns — the kind you don't normally expect from typical development — are a good reason to check hearing. A child can only copy the sounds they're actually hearing, and sometimes those patterns are a clue that something's getting in the way.
What Should You Do If You're Concerned?
If your child is hard to understand and you've noticed patterns that seem unusual — sounds being replaced in unexpected ways, or errors that don't seem like the typical "cute" speech of a young child — it's worth having an assessment.
Early identification of atypical speech sound patterns means we can start the right kind of therapy sooner, which leads to better outcomes for your child's speech clarity, confidence, and literacy development.
Frequently Asked Questions
Q: How do I know if my child's speech errors are atypical or just delayed?
A: One common approach to find out is through a thorough speech pathology assessment. Delayed patterns are ones that all children use at some stage but should resolve by a certain age. Atypical patterns are ones that aren't part of typical development at all. A speech pathologist can analyse your child's speech and tell you which category their errors fall into.
Q: Will atypical speech sound errors go away on their own?
A: Unfortunately, atypical patterns are much less likely to self-correct than delayed ones. Research consistently shows that children with atypical errors need targeted intervention to make progress. The sooner these patterns are identified, the better the outcomes.
Q: Does my child need a different kind of therapy for atypical errors?
A: Yes — and this is exactly why getting the right assessment matters. Atypical errors often respond to different therapy approaches than delays. For example, core vocabulary therapy may be more effective than minimal pairs for some children with atypical or inconsistent errors.
If your child's speech errors don't seem to follow the usual patterns, a thorough assessment is the best next step. We use Dodd's classification system to work out exactly what's going on and match the right therapy to your child's needs. Speaking Speech Pathology offers mobile speech pathology in your home across Brisbane's south side and Logan — get in touch to find out more. Any actual clinical work — assessment, diagnosis, or therapy — happens through a proper consultation tailored to your child.
Ready for practical strategies? Read our companion article: Therapy for Atypical Speech Sound Errors: Evidence-Based Approaches in Brisbane
Alexandra Bouwmeester is a Senior Speech Pathologist (MSPA, CPSP) with over 14 years' experience assessing and treating speech sound difficulties. She uses Dodd's classification framework to ensure every child receives therapy matched to their specific profile.
References
- Dodd, B. (2014). Differential Diagnosis and Treatment of Children with Speech Disorder (2nd ed.). Whurr Publishers.
- Broomfield, J., & Dodd, B. (2004). Children with speech and language disability: Caseload characteristics. International Journal of Language & Communication Disorders, 39(3), 303–324.
- Crosbie, S., Holm, A., & Dodd, B. (2005). Intervention for children with severe speech disorder: A comparison of two approaches. International Journal of Language & Communication Disorders, 40(4), 467–491.
