Every child is unintelligible for at least three years, but some are unintelligible for longer. The underlying root of the speech sound disorder may give us an idea of your child's intelligibility potential. However, we often don't know the cause. Speech sound disorders are one of the most studied aspects of Speech-Language Pathology, so we can give you a good set of numbers for comparison. The numbers are evidence-based but they shouldn't be seen as a description of where your child should be. Every child is different. Every prognosis is different. Use these numbers to have a conversation with your Speech-Language Pathologist.
With speech-sound disorders, you will typically find problems acquiring a sound, problems with patterns of speech, problems with intelligibility, and some differences with children who are bilingual or from a background different than the background of the SLP. We've outlined some of the common areas we examine below.
When should you be concerned about your child's wabbit?
A child's phonetic inventory isn't fully developed until they are about eight years old. Speech sounds are acquired at different ages based on your child's gender and background. /r/ is, hands-down, the absolute hardest sound for kids to acquire. It will most likely be the last sound your child acquires. Lawrence Shriberg, one of the most prestigious researchers in Speech-Language Pathology, developed a framework most SLP's loosely follow. The following is adapted from Shriberg's Order of Speech-Sound Acquisition (1993).
Early Eight Sounds. Your child's sound inventory begins to emerge when they are one to three years old. By three, they've pretty much mastered eight sounds. These are the sounds they master first:
- /m/ as in "mama"
- /b/ as in "baby"
- /n/ as in "no"
- /j/* as in "you"
- /w/ as in "we"
- /d/ as in "daddy"
- /p/ as in "pop"
- /h/ as in "hi"
Middle Eight Sounds. The middle eight sounds are developed when your child is between three to six and a half years old. It is not uncommon to see mastery and consistency at five, but six and a half is where you'll see that most of the kids in a cohort level out.
- /g/ as in "go"
- /k/ as in "cup"
- /t/ as in "two"
- /f/ as in "fish"
- /ŋ/ as in the "ng" in "running"
- /v/ as in "van"
- /tʃ/ as in the "ch" in "chew"
- /dʒ/ as in the "j" in "jump"
Late Eight Sounds. The late eight sounds begin emerging when a child is about five years old. They're typically consistent by the time a child is seven and a half.
- /s/ as in "see"
- /θ/ as in "th" in "think"
- /ð/ as in "th" in "that"
- /ʃ/ as in "sh" in "sheep"
- /r/ as in "red"
- /z/ as in "zoo"
- /l/ as in "like"
- /ʒ/ as in "zh" in "measure"
*When you see a letter in between slashes, we are referring to the sound. The letter and the sound don't always match up with what you're used to seeing in the alphabet.
We like it that Schriberg breaks sound acquisition down into eight easy to understand chunks so we use that as a baseline for a quick reference. When we see more variability in acquisition, we consult some common exceptions. For example, girls typically acquire sounds differently than boys. These norms below are from the Nebraska-Iowa Articulation Norms Project and are considered the standard in our industry.
Typical Acquisition for Girls
- Age 3: /b/ /p/ /m/ /n/ /h/ /w/ /d/ /k/ /f-/** /g/
- Age 4: /t/ /j/ /ð/ /tw/ /kw/
- Age 5: /v/ /-f/ /l-/ /pl/ /bl/ /kl/ /gl/ /fl/
- Age 6: /ʃ/ /dʒ/ /tʃ/ /θ/ /-l/
- Age 7: /z/ /ŋ/ /s/ /sp/ /st/ /sk/ /sm/ /sn/ /sw/ /sl/ skw/ /spl/
- Age 8: /r-/ /pr/ /-er/ /br/ /tr/ /dr/ /kr/ /gr/ /fr/
- Age 9: /thr/ /spr/ /str/ /skr/
Typical Acquisition for Boys
- Age 3: /b/ /p/ /m/ /n/ /h/ /w/ /d/ /k/ /f-/ /t/
- Age 4: /g/
- Age 5: /j/ /tw/ /kw/ /v/ /f/
- Age 6: /l-/ /pl/ /bl/ /kl/ /gl/ /fl/
- Age 7: /ð/ /z/ /ŋ/ /s/ /sp/ /st/ /sk/ /sm/ /sn/ /sw/ /sl/ skw/ /spl/ /ʃ/ /dʒ/ /tʃ/ /-l/
- Age 8: /θ/ /r-/ /pr/ /-er/ /br/ /tr/ /dr/ /kr/ /gr/ /fr/
- Age 9: /thr/ /spr/ /str/ /skr/
**When you see a - before or after a letter that means the sound can be pronounced in the initial /f-/ or final /-f/ position of a word. The placement in the word can sometimes make the pronunciation of sounds tricky.
Patterns in Speech
When will my child's nana turn into banana?
There are often patterns to a speech sound disorder, these patterns are called phonological processes. SLPs are trained to recognize the pattern and treat at the root of the problem. We consider (1) assimilation, (2) substitution, and (3) syllable structure patterns when we look at the speech sound development of a child.
When one sound becomes the same or similar to another sound in the word. Assimilation is sometimes referred to as Consonant Harmony (although we prefer assimilation). There are two types of assimilation:
Velar Assimilation: non-velar sounds become velar because they are close to a velar sound. e.g., kack is pronounced, but the target was tack.
Nasal Assimilation: non-nasal sounds become nasalized because of their proximity to a neighboring nasal sound. e.g., munny is produced instead of funny.
When one sound is substituted for another sound in a systematic way. There are seven types of substitutions:
Fronting: a sound that is made in the back of the mouth (velar) is made in the front of the mouth (alveolar). e.g., the child attempts to say car, but they say tar. This typically disappears by the time the child is four years old.
Deaffrication: an affricate is replaces with a fricative. e.g., shop is said instead of chop. This typically disappears by the time the child is five years old.
Gliding: a liquid is replaced with a glide. e.g., wabbit is said instead of rabbit. L glides typically disappear by the time the child is five, but r glides are persistent until a child is about seven.
Backing: a sound that is made in the front of the mouth is made in the back of the mouth. e.g., tar is the target, but the child says car. This typically disappears by the time the child is four years old.
Stopping: a fricative or affricate sound is replaced with a stop sound. e.g., tee is used instead of see. This typically disappears by the time the child is four years old.
Postvocalic devoicing: the child devoices a consonant sound (that should be voiced) after pronouncing a vowel. e.g., a child says tab when they intend to say tap. This typically disappears by the time the child is five years old.
Prevocalic voicing: the child voices a consonant sound (that should be devoiced) before a vowel. e.g., the child says ban when they should say pan. This typically disappears by the time the child is four years old.
Some sound changes will impact the syllable structure in the word. There are three of these to consider:
Cluster reduction: a consonant cluster is simplified into a single consonant. e.g., top for stop. Cluster reduction can happen in the initial, medial, or final position of a word. Initial cluster reduction typically disappears by the time the child is five years old, final cluster reduction typically disappears by the time the child is six years old, and medial cluster reduction typically disappears by the time the child is seven and a half.
Weak syllable deletion: the unstressed or weak syllable in a word is deleted. e.g., nana for banana.
Final consonant deletion: the deletion of the final consonant in the word. e.g., bu for bus. This typically disappears by the time the child is three years old.
This list of patterns were pulled from Bauman-Waengler's Articulatory and phonological impairments (2012) and Bernthal, Bankson & Flipsen's Articulation and phonological disorders (2013). The age range for the disappearance of phonological processes was adapted from Webb and Duckett's Rules Phonological Evaluation (1990).
Norms for the bilingual or culturally diverse child
Yes, it's sometimes okay for your child to say ban for van.
Some Spanish dialects do not use the phonetic sound of /v/. Therefore, it is not uncommon for a child from a Spanish background to not hear the difference between a /b/ and /v/ sound, thus resulting in the acceptable substitution of ban for van.
A single SLP cannot be an expert on every dialect and language in the world. Luckily, we've got the American Speech-Language and Hearing Association (ASHA) to help. ASHA has a collection of phonemic inventories from Amharic to Vietnamese, a bilingual service directory, and tips for collaborating with interpreters.
ASHA has a lot of information on cultural norms and can be a great resource for the school-based SLP in a culturally diverse community. In fact, ASHA has an Office of Multicultural Affairs and Resources to help all SLPs with awareness of cultural diversity.
It is important for an SLP to know a child is bilingual if they are assessing or treating them. For example, most bilingual children begin acquiring sounds and speaking slower than monolingual children. The late talking doesn't mean there is a problem, it just means they are figuring out two languages at once!
Similarly, there are regional, socioeconomic, ethnic, and cultural variations of American English that should not be corrected. Your SLP will be adept in parsing a disorder from a difference. Please ensure you discuss any concerns you have about language differences with your SLP.
Accuracy does not equal Intelligibility
Although children aren't acquiring adult-like sounds until they are eight, they are able to make approximations that (within the context of words, sentences, and conversation) sound pretty close to the intended target. When someone says wabbit instead of rabbit, we understand what they are saying, we just interpret their speech as child-like (even if all of the other sounds in their inventory are correct). If a child is missing several sounds, or unable to produce longer utterances, it is difficult for listeners to understand what they are saying. When someone is under 80% of intelligibility, listeners are relying on something else to understand the intended message. Based on the sound acquisition in the chart above, you can start to guesstimate intelligibility based on age:
- A one-year-old child should be 25% intelligible.
- A two-year-old child should be 50% intelligible.
- A three-year-old child should be 75% intelligible.
- A four-year-old child should be 100% intelligible.
You're probably thinking, "Hold up. You said kids can't get all their sounds until they are eight. How are they intelligible at four?" By the time a kid is four, their utterances are long enough for communication partners to figure out what they are saying based on context clues in the conversation.
- a one-year-old says one-word utterances.
- a two-year-old strings together two-word utterances.
- a three-year-old strings together three-word utterances.
- a four-year-old is doing four-word utterances and moving on into more complex sentences.
Your SLP will determine the intelligibility level, for an unfamiliar listener, as part of their assessment.