As speech-language pathologists, we are well versed in phonological delays. We know what fronting looks like, we can spot cluster reduction from across the room, and stopping barely makes us blink. But what happens when a child’s errors don’t fit the familiar developmental map? What happens when the errors aren’t just delayed – they’re different?

Atypical phonological processes are a clinically distinct presentation that requires its own assessment considerations and a heightened level of vigilance about long-term outcomes. This blog covers what atypical phonological errors are and how to assess for them accurately. Part two of this series will turn to treatment.

What Are Atypical Phonological Processes?

A phonological delay occurs when a child produces error patterns that are typical of younger children – patterns that are part of normal speech development but are persisting longer than expected. Examples include:

• Fronting (e.g., key → tea)
• Stopping (e.g., fun → bun)
• Cluster reduction (e.g., spoon → poon)

Atypical phonological processes, by contrast, are error patterns that do not occur at any stage of typical speech development. They are not simply delayed — they are outside the developmental sequence entirely. Examples include:

• Backing – an alveolar sound produced further back (e.g., tea → key)
• Initial consonant deletion – the first consonant is omitted (e.g., cat → at)
• Gliding of fricatives – fricatives are replaced by glides (e.g., fun → wun)
• Initial consonant devoicing – voiced initial consonants become voiceless (e.g., bat → pat)
• Final consonant voicing – voiceless final consonants become voiced (e.g., hop → hob)
• Nasalisation – oral consonants are replaced by nasals (e.g., top → nop)

These errors are not simply “more severe” versions of typical errors. They represent a different pattern of speech production that has distinct clinical implications.

Why It Matters: The Downstream Risks

The significance of identifying atypical phonological errors goes well beyond speech production. Research by Roepke et al. (2026) found that when compared to children with typical phonological errors, children who produce atypical phonological errors have significantly more difficulty with:

• Phonological awareness – the ability to identify and manipulate sounds in words
• Literacy – reading and writing development
• Executive function – cognitive skills like working memory, cognitive flexibility, and inhibitory control
• They are also more likely to have persistent errors that do not resolve without targeted intervention

This means that a child with atypical phonological errors is not simply a child who will “catch up.” The watch-and-wait approach, which might be appropriate in some cases of mild phonological delay, is not appropriate here. Early, accurate identification and prompt treatment are essential.

Getting the Assessment Right

Accurate assessment is the foundation of good intervention. Atypical errors are easy to misidentify — and misidentification leads to the wrong treatment. Here are the key principles to follow.

1. Make Sure the Child Said the Target Word

This sounds simple, but it is easy to overlook. Before you can classify an error, you need to be certain you heard what the child intended to say.

Use yes/no questions to confirm: “Did you just say helicopter?” If yes/no responses are inconsistent, try a direct prompt: “Can you say helicopter again? I didn’t have my listening ears on.” This simple step can prevent you from marking an error that wasn’t actually an error.

2. Consider Dialect, Idiolect, and Multilingual Influences

Not every non-standard production is a disorder. Before labelling something as an atypical pattern, consider:

• Dialect: Productions may be a consistent feature of a regional or cultural dialect, rather than errors.
• Family or home language patterns: If an entire family produces library as libary, this is unlikely to reflect a phonological disorder.

Errors must be systematic to constitute a phonological process. Always contextualise findings within the child’s linguistic environment.

3. Analyse Errors Across Multiple Words

A phonological process, by definition, is a pattern. You cannot identify a pattern from a single word. Analyse a variety of words before drawing any conclusions about error type, and resist the temptation to name a process based on limited data.

4. Rule Out Assimilation

Assimilation – when a sound takes on features of a neighbouring sound – is considered a typical process and should not be categorised as an atypical error. For example, /gʌk/ for duck could reflect backing, or it could reflect assimilation to the final velar. You need sufficient data to distinguish between the two.

Pay particular attention to alveolar stops, as these are the most likely to assimilate to other sounds in the word. Include enough words containing alveolar stops in your assessment to properly evaluate this.

5. Examine Error Consistency

This step is critical and often overlooked: inconsistent phonological disorders can look like atypical phonological disorders, but they are not treated the same way.

Screen for whole-word variability by having the child produce a set of words three times across the session, with a break between each production set. Inconsistent production of the same word across attempts is a marker of inconsistent phonological disorder and it changes your treatment pathway significantly.

6. Consider Motor Speech

Phonology and motor speech exist on a continuum and frequently overlap. Some oral motor difficulties may co-occur with a phonological disorder and do not rule one out. However, if a child is showing clear signs of childhood apraxia of speech (CAS), this should be treated first.

Crucially, inconsistent errors are a feature of both inconsistent phonological disorder and CAS. Your consistency probe data, combined with a thorough motor speech assessment (e.g. the DEMSS), will help you differentiate.

7. Factor In Age and Vocabulary Size

Phonological patterns become more predictable once a child has an expressive vocabulary of 50 words or more. Attempting to identify phonological patterns in a child with fewer words than this is unlikely to yield reliable results.

For children over 24 months with more than 50 words, current evidence suggests that two or more atypical patterns should raise a suspicion for speech sound disorder. A single atypical pattern at this age, in isolation, is not necessarily a clinical concern.

What’s next?

Getting the assessment right is an important first step. Once atypical patterns are accurately identified – and assimilation, inconsistent phonological processes and dialectal/family pronunciation have been ruled out – the path to treatment becomes much clearer. In part two of this series, I’ll walk through the evidence-based treatment approaches for atypical phonological errors, including why watchful waiting has no place here and how target selection differs from a typical phonological caseload.  

Reference:

Watson, L. (2026) Not your typical speech sound errors. The Informed SLP