Children’s speech development typically follows a predictable course even for children learning different languages: 

• speech-like sounds are produced in babble at approximately 7 months
• recognizable words are spoken at 1 year 
• consonants, vowels and tones are learned (perception and production) between 2 to 5 years 
• intelligible (understandable) sentences are communicated with sentences by 4 to 5 years
• speech development is concluded by 8 to 9 years. This includes all consonants, vowels, tones in types of syllables(including consonant clusters), long words (polysyllabic words) with the correct rhythm, stress, and intonation of the child’s language on a consistent basis. 

Although children differ from each other in the way that that they speak, these milestones should be achieved at the expected ages. When these milestones are not achieved, a speech sound disorder may be diagnosed. 

The reasons for a speech sound disorder are often hard to identify because speech is complex, involving many structures and processes. For many children, there is no known cause (even without a known cause there are many successful evidence-based interventions).

Known causes can be linked to the structure and function of the mouth (lips, teeth, palate, tongue), nose and ears, larynx (voice box), lungs, nerves, and brain since these impact speaking. Certain developmental disorders may explain speech disorders such as: cerebral palsy which impairs muscle function and often results in dysarthria, cleft palate which impairs the flow of air through the mouth, tongue tie which might impact the range of motion of the tongue, dental anomalies that might make it difficult to articulate speech sounds correctly. These disorders are rare however and are relatively easy to identify. There may be subtle differences in the development of brain structures thatimpair the ability to coordinate speech movements–the resulting speech sound disorder. For example, childhood apraxia of speech (CAS), is difficult to diagnose but treatable with intense speech therapy. 

Speech sound development also requires intense listening. Children must learn which speech sounds are used in their language, and how those sounds are combined to create words, by attending to speech input from people around them. Hearing impairments, even the mild hearing impairment associated with chronic ear infections (otitis media/glue ear), can impact speech development. Sometimes children can hear sound perfectly but do not process speech input reliably and therefore have difficulty learning the speech sound system of the ambient language. For example, the child might not be sure whether similar words such as “tart” and “cart” mean the same thing ordifferent things. This kind of phonological processing disorder is often hereditary and is associated with problems in speech and reading development. It can be frustrating to not know the cause of your child’s speech sound disorder but effective speech intervention approaches can be applied even when the cause is uncertain.

Parents are the most important influences in children’s environments for promoting good speech development. Children learn speech by listening and by having good conversations. Parents are in the best position to talk with their children about topics that interest them. Adults can talk about what children are seeing and doing when they are are jointly engaged in the same activity. Everyday routine activities are perfect because children will hear the same words many times, and repeated in more complex sentences as time goes by. Bathing, making breakfast, getting ready for school, playing: all these daily activities are opportunities for rich conversations. Sharing picture books is an especially valuable activity for talking together: besides reading the story, talk about the pictures, respond to your child’s questions and comments, ask your child questions, and connect the story to your child’s own experiences. If you are concerned about your child’s pronunciation of a specific sound–perhaps your child says “wam” instead of “lamb”, you could share books or rhymes about lambs. However, it is best to use the book as an opportunity to model the difficult sound; do not try to teach your child correct pronunciation unless a speech therapist has advised you to practice saying the sound with your child. Therefore, you might have conversationslike this:

Parent: Look at all the animals in the field! How many lambs?

Child: One.

Parent: That’s right, one lamb. And on this page, how many lambs?

Child: Two wambs.

Parent: Yes, I see two lambs, one lamb, two lambs. A white lamb and a black lamb. Remember we saw a black lamb at the petting zoo?

In this example the child hears the word “lamb” said correctly many times. He is engaged in the conversation but is not pressured to speak correctly or embarrassed by errors. Overtime he will notice the difference between his own incorrect production and adult correct productions. This listening experience may help him learn to correct his pronunciation.

If your child is older and is continuing to misarticulate certain speech sounds, you might ask your child to engage in certain prereading activities while listening to sounds. For example, your child might say the “s” sound in a way that is distorted or slushy. Even with the older child, the opportunity to hear many good examples of the difficult sound will be valuable. You might cut out pictures together of words that start with different sounds such as “f” (feather, fish, forest), “th” (think, thorn, theatre), and “s” (saw, sand, soap). Ask your child to paste the pictures on to different pieces of paper marked with the appropriate letters. Alternatively, you might find pictures of words that start with “s”(saw, sand, soap) or end with “s” (bus, mouse, house);  cut these out and paste them onto the right and left pages of a notebook. The idea is to give your child opportunities to listen carefully for the sound and decide which sound is which or where the sound is. Once again, do not practice speech production without the help of a speech-language pathologist. If your child does not seem to be improving, a speech-language pathologist can help you and your child with more specialized procedures.

The age at which children should be using all the adult consonants, vowels (and tones) can be influenced by the language/s they are exposed to. However, overall most consonants, vowels and tones are learned by 5 years of age (McLeod & Crowe, 2018). The rate and route of speech sound development for monolingual children may be different from that of multilingual children. In general consonants that are produced earlier are nasals (e.g., m, n, ng) and stops (e.g., b, p, t, d, k, g).  Consonants that typically are produced later are fricatives (e.g., s, sh, th), affricates (e.g., ch, ts) and liquids (e.g., r).

Children who are exposed to bilingualism early on, are at an advantage, both in terms of speech and language skills and cognition. When children are exposed to more than one language from birth they can become proficient in these languages, as long as they receive consistent and abundant exposure to both. Think about children’s language exposure can in terms of person, place and time.

Children who start school with unresolved speech difficulties may have challenges in the school system. They may find it hard to communicate their needs to teachers and peers, may struggle with social aspects (e.g., making friends), and may have difficulty learning to read and write. Spoken language and literacy are linked to each other: spoken language is the foundation of the skills needed for reading and spelling. Speech sound disorders are often the result of a speech system that is immature or not developing in the usual way. This speech sound system is also the basis for a child’s reading and spelling, as they must make links between sounds that are heard or produced and the symbols on the page. 

Phonological awareness – the ability to reflect on, identify and manipulate the sounds of language/s – is a good example of a skill that is closely linked to both speech and literacy. For example, identifying that there are three sounds in the word “dog”  (d – o – g) AND “sheep” (sh – ee –p) requires phonological awareness; children with speech sound disorders may have difficulty performing such tasks. The nature and extent of a child’s speech difficulties do not always predict the type of experience they have at school. What is clear is that children with speech sound disorders benefit from early intervention in the preschool years, and if a child starts formal schooling with unresolved speech difficulties it is important that they receive support to address their communication challenges and any related literacy, academic and social issues.

McLeod, S., & Crowe, K. (2018). Children’s consonant acquisition in 27 languages: A cross-linguistic review. American Journal of Speech-Language Pathology, 27(4), 1546–1571. https://doi.org/10.1044/2018_AJSLP-17-0100