HELP! My child has a lisp

We hear this comment frequently from parents, often with kids ranging from 2 years up to 8 years of age. What is a lisp? When it is normal? When should it, if at all, be treated?

What is a lisp?

A “lisp” usually refers to a person’s difficulty producing the /s/ and /z/ sounds because of incorrect tongue placement. It is a ‘functional speech disorder’ as the cause is usually unknown. The tongue may be sticking out between the front teeth, or the sides of the tongue may not be high enough or tense enough in the mouth. Both of these articulation errors result in sound distortions, giving it the distinctive ‘slushy’ sound.

How the “s” and “z” sounds are made…

Before you work out whether your child has a lisp and where they’re going wrong, it’s helpful to know how we actually make the correct /s/ and /z/ sounds.

You may be surprised to learn that /s/ and /z/ are essentially the same sound. The positioning of your lips, tongue and teeth are the same for both. The tongue is kept behind the teeth, with the tip of the tongue either behind the top or bottom teeth. The sides of the tongue are curved upwards to touch the upper molars. This results in the tongue forming a groove down the middle, which the airflow passes through to produce the sound.

The only difference between the production of /s/ and /z/ is whether we use our voice or not. The /s/ is what we called a “voiceless” sound, where the “hissing” sound you hear is the air escaping from your mouth. On the other hand, “z” is a “voiced” sound because the voice is turned on, which simply means that our vocal folds start vibrating to produce the sound.

Four Types of Lisps


  1. Interdental (frontal) lisp

This occurs when the tongue pokes out between the front teeth and airflow is directed forwards. This makes a /s/ or /z/ sound like a /th/. For example,  sock” becomes “thock” and “zoo” becomes “thoo”.

  1. Dentalised lisp

In this type of lisp, the tongue rests on or pushes against the front teeth and airflow is directed forwards, producing a slightly muffled sound.

  1. Lateral lisp

This occurs when the tongue lies flatter in the mouth, which directs airflow over and out the sides of the tongue. Lateral lisps are often called “slushy” as they sound “wet” and “spitty”– think Sylvester the cat!

  1. Palatal lisp

In this type of lisp the mid section of the tongue comes into contact with the soft palate. Caroline Bowen (an Australian speech pathologist and speech sound guru!) explains that if you tried to produce an “h” closely followed by a “y” sound, you would more or less have an example of what a palatal lisp might sound like.

Is a lisp ever normal?

Interdental and dentalised /s/ and /z/ sounds are a common developmental phase for most children, up until 4 1/2 years of age. If the error persists, it is recommended that you seek advice from a speech language pathologist who can assess your child and determine if intervention is required.

Lateral and palatal lisps however, are NOT part of normal development and should be assessed by a speech language pathologist.

A few tips for lisps

We cannot give specific advice through our blog without seeing and hearing your child however here are a few things parents can try with their child if they are struggling with a interdental or dentalised /s/ and /z/ sound.

  • Verbal prompts: tell your child what their lips, mouth, tongue need to be doing. For example, teeth together, tongue behind your teeth (just touching your teeth) and smile.
  • Visuals prompts: stand side-by-side in front of a mirror, show your child how you would make the sound.
  • Keep it positive: Instead of telling your child, “No, that’s not how you say it.”, repeat what they’ve said but with the correct sound production. This acknowledges that you have still understood your child’s message but you are also providing a positive model of the correct way to say the sound.

Just remember, if you need more specific advice about your child, it is best to see a qualified speech language pathologist. You can find one locally through Speech Pathology Australia –

References: numbered list

    1. Bowen, C. (2011). Lisping: When /s/ and /z/ are hard to say. Retrieved from on 10.04.2018.


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