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The 4 Types of Lisps Explained

Updated: Feb 9

A person has a lisp when they cannot correctly pronounce the /s/ and /z/ sounds. This common type of functional speech disorder affects many children and adults.


Usually, the lisp develops in early childhood and goes away on its own as the child grows up, but some people have a lisp throughout their lives. There are 4 types of lisps: interdental, lateral, dentalized, and palatal. 


Read on to understand more about the different types of lisps, their causes, and how lisps are treated.





The Four Types of Lisps


Lisps are the result of incorrect placement of the tongue inside the mouth. To pronounce the /s/ sound clearly, the tip of the tongue should be just behind the front teeth in a bumpy part of the mouth called the alveolar ridge, close to the roof of the mouth but not touching it.


The sides of the tongue are raised toward the roof of the mouth. There should be room down the middle of the tongue for air to travel. The teeth should be together, and the lips should be slightly parted with the corners upturned slightly. 


/S/ sounds are unvoiced and are created completely with the shape of the passageway you create with your mouth and teeth. Any differentiation in this formation can cause a lisp. Many children have difficulties with the /s/ sound in their early speech development. Most children master the /s/ and /z/ sounds by the time they are 5 years old. 


There are many kinds of lisps. This articulation problem can be frustrating and embarrassing for children and adults. Understanding the most common types of lisps will help you to understand what causes your child’s condition so you can better know how it will be treated.


#1 Interdental Lisp


An interdental lisp, also called a frontal lisp, is the most common type of lisp. This lisp is caused by the tongue pushing forward between the teeth, creating a /th/ sound in place of the /s/ sound. This type of lisp is sometimes caused by a tongue thrust. A tongue thrust is an orofacial disorder when a child has an abnormal tongue position.


Children with a tongue thrust may have issues with eating and drinking as well as speaking. Prolonged thumb sucking, pacifier use, allergies, and mouth breathing can also cause this issue. When the tongue constantly sits too far forward, it presses the tongue between the teeth causing the interdental lisp. 


A child with tongue thrust needs to see a dentist, orthodontist, and speech pathologist in tandem to create a comprehensive treatment to address the needs of this condition. Many tongue thrusts resolve by age six on their own, but some continue to persist.


 However, not all interdental lisps are a result of a tongue thrust. 


#2 Lateral Lisp


A lateral lisp is when the tongue is almost in the correct position, but the sides of it are not high enough in the mouth. The sound a child produces with this type of lisp is a slushy, wet sound when the /s/ or /z/ sound is made. Air escapes to the sides of the mouth rather than flowing down the middle. 


This type of lisp is often the result of incorrect tongue placement. Teeth misalignment and weak mouth muscles may also cause a lateralized lisp. Sometimes a combination of these issues is the cause. 


If your child places their tongue between their teeth while making the /s/ or /z/ sounds or their teeth seem to be placed in the wrong position, then your child may have signs of a lateral lisp. 


You will need to work with a speech-language pathologist (SLP), dentist, and orthodontist to correct a lateral lisp.


#3 Dentalized Lisp


The dentalized lisp, or addental lisp,  is similar to the interdental lisp. In this case, the child pushes their tongue against the front teeth when making the /s/ or /z/ sound. This differs from the interdental lisp, where children push their tongue through their front teeth when forming these sounds. 


The sound produced by a dentalized lisp sounds like a muffled /s/. Many children have dentalized lisps when they are younger but eventually grow out of the y around 4-5 years of age. However, if a child is still lisping at age 7 or if you feel the lisp is problematic, it is important to have a speech-language pathologist evaluate and treat the articulation error.


#4 Palatal Lisp


The least common type of lisp is the palatal lisp. This type of lisp is when the tongue raises to the hard or soft palate when making the /s/ or /z/ sound. The tongue blocks the air flow causing a muffled sound that mimics the /h/ or /y/ sounds. This speech sound is not a normal part of speech development.


If your child has a palatal lisp, experts advise you to seek out an SLP as soon as possible for evaluation. A speech-language therapist can test your child for speech therapy and treat the lisp before it is too late to correct this speech error. 


What Causes Lisps?


Some lisps may be the cause of a tongue tie (ankyloglossia) which is a condition where a band of tissue connects the underside of the tongue to the floor of the mouth. The tongue is unable to move freely with this condition. Tongue ties are formed before a baby is born. The tissue connection usually goes away as the baby develops. 


However, sometimes the tissue, called the frenulum, may be too short or tight and stay near the tip of the tongue. It can cause issues with eating and a child’s speech. Often, tongue ties are diagnosed while a child is still a baby and the issue is corrected with a simple procedure where the frenulum is released with a scalpel. 


Still, some milder tongue-ties may not be detected until the child is much older. Older children often have to undergo surgery to free the frenulum. A tongue tie can result in a speech delay if it is left untreated. 


Lisps can also be a result of genetics. The development of a person’s jaw, teeth, tongue, and bit can cause a lisp. Abnormalities of these mouthparts make it difficult for a child to produce the desired sounds. Oftentimes, these types of issues may need surgery for correction. 


Also, children with mild hearing loss may hear sounds at different frequencies, which can affect their ability to hear and repeat sounds correctly.


Most lisps are the result of a phonetic disorder. The person simply struggles to position their tongue, lips, teeth, and jaw correctly. A person can make the sounds, but they struggle to achieve these sounds without speech therapy.


In some cases, the cause of a lisp may be a combination of the above factors. 


Treatment for Lisps


The treatment for lisps varies based on the cause of the lisp. Some frontal lisps are simply a part of a child’s normal speech development and they will eventually grow out of it. According to the SLP's evaluation, some young children may simply be placed under observation. 


Most lisps are treated with an SLP over a few months to a few years. The older the child is once the intervention begins, the longer the treatment typically takes. A speech pathologist will work to help people with lisps recognize the sounds they make and be more aware of the position of their tongue.


During speech therapy, your child will work on intelligibility. They will practice placing the tongue in the correct place to make the /s/ and /z/ sounds. SLPs give children exercises that involve saying words and phrases over and over as part of their language therapy. They may start by working on correcting single words, first.


If your child’s lisp is the result of a dental or tongue issue, they may also need to see a dentist, orthodontist, or otolaryngologist (ears, nose, throat doctor) to help correct any obstructions to correct tongue and teeth formation.





Other Similar Speech Impediments


Many types of speech impediments affect the way a child produces sounds. Two other common ones include lambdacism and rhotacism.


With lambdacism, a child has trouble saying the /l/ sound. They often substitute that sound with the /r/ sound. Rhotacism is when a child has difficulty pronouncing the /r/ sound. The /r/ sound is one of the most challenging letters to pronounce in the English language.


There are over 32 variations on how to produce the /r/ sound. Many children have difficulty with this sound. Rhotacism is identified when a child makes a vowel-like sound or a /w/ sound instead of the /r/ sound. 


The causes of these types of speech impediments are similar to those of a lisp. It may simply be a placement issue with the tongue and mouth or there could be something such as a tongue tie obstructing the sound production. Evaluation by a speech-language pathologist will help you understand these conditions and how to treat them. 


However, children can have issues pronouncing many different letter sounds including /k/,/g/, /t/, /d/, and /e/, as well. 


How to Prevent a Lisp


You cannot always prevent children from developing a lisp. However, there are some ways you can encourage mouth muscle strength and treat issues that may lead to a higher risk of developing a lisp.


Thumb sucking can lead to dental issues or tongue placement issues that may cause a lisp. It is ideal to discourage your child from sucking their thumbs. Pacifiers can also become a problem if your child uses them for a prolonged time. The American Academy of Pediatric Dentistry suggests weaning a child from a pacifier by the time they are 3 years old.


Encouraging your child to drink through a straw, blow bubbles, and play with horns will build muscle strength in the mouth that will aid in strengthening the muscles needed for producing the /s/ and /z/ sounds.


Finally, if your child has allergies and sinus problems, these may eventually lead to a lisp. It is key to seek out a medical professional to best treat your child for these issues to reduce their chances of having speech development issues. 


If you suspect any delays in speech or speech errors, it is better to seek out a medical professional than to continue to worry whether or not it may be an issue. A speech-language therapist can evaluate and treat children for a variety of speech, language, voice, and learning disorders.


Looking For A Speech Therapist to Correct a Lisp


Finding the right speech-language pathologist to help your child can be a big task. You may wonder if your insurance will cover the cost or if you’ll be able to afford to get your child the therapy he or she needs.


The California Scottish Rites Foundation is dedicated to supporting and assisting children in California by providing childhood speech-language, literacy, and education programs at no cost. We have 17 Rite Care locations throughout California to serve communities throughout the state.


Our SLPs are trained professionals who offer individualized services that address the needs of developing children and their families. They not only help with speech, language, and education, but they also help empower children by increasing independence, decreasing frustrations, and leading children down a pathway to academic success.


Conclusion


A lisp is a common functional speech disorder that affects the articulation of the /s/ and /z/ sounds your child makes. The earlier this condition is detected, the easier it is to correct. The four major types of lisps: interdental, lateral, dental, and palatal are characterized by the placement of the tongue and the flow of air through the teeth. 


Lisps are treatable with the aid of a speech-language pathologist who will help coach your child on how to position the tongue to correctly pronounce the sounds. If your child’s lisp is caused by an issue with the teeth, tongue, or mouth, dentists and other specialists can help correct these issues alongside speech therapy to correct a lisp.


The earlier you seek assistance for your child, the better the outcome on their speech development.



 





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