Types of Lisps: How to Identify and Address Them
If the /s/ or /z/ sound comes out as a soft "th," a slushy hiss, or a muffled buzz, you are likely hearing a lisp. A lisp is one of the most common reasons people seek speech therapy, and it can affect both young children and adults.
Once a speech therapist identifies the kind of lisp you are hearing, the path forward gets much clearer. The guide below walks through the four types of lisps, how to tell them apart by sound and tongue placement, what causes them, and when it helps to see a speech therapist.
Key Takeaways
A lisp is a speech sound disorder that changes how /s/ and /z/ sounds are produced. It happens when the tongue is placed incorrectly, or airflow is directed the wrong way. The four main types of lisps are interdental, dentalized, lateral, and palatal. They are classified by tongue placement and airflow patterns.
You can often identify the type of lisp by how it sounds. An interdental lisp typically makes /s/ and /z/ sound like "th." A dentalized lisp produces a muffled /s/. A lateral lisp creates a slushy or wet-sounding /s/, while a palatal lisp produces a sound that is both muffled and slushy.
Interdental and dentalized lisps are common in young children and often resolve as speech develops. Lateral and palatal lisps are not part of typical speech development and usually warrant evaluation by a speech-language pathologist.
Speech therapy can help correct a lisp at any age. A speech-language pathologist works on tongue placement, airflow control, and sound production through structured practice. Earlier intervention often leads to faster progress.
When to See a Speech-Language Pathologist
What We See Working With Clients
What Is a Lisp?
A lisp is a speech sound disorder that affects how a person produces the sibilant sounds /s/ and /z/. The condition changes the way airflow and tongue placement shape these sounds, which can make speech sound distorted. Both learned speech patterns and anatomical factors can contribute to a lisp.
A clear /s/ sound requires the tongue tip to rise toward the alveolar ridge, the small ridge behind the upper front teeth. Air then travels in a narrow stream down the center of the tongue. When the tongue sits in the wrong position or air escapes in the wrong direction, the result is a lisp.
A lisp reflects a learned speech pattern, not a lack of effort. Because the problem involves placement and airflow, it often responds well to speech therapy and targeted practice. Identifying the specific type of lisp helps a speech-language pathologist choose the most effective treatment approach.
How a Lisp Affects Communication
A lisp does not affect everyone the same way. Some people view it as a minor speech difference, while others feel it affects their confidence or ability to communicate clearly. A 2020 article in Speech Pathology Graduate Programs noted that approximately 23% of people seek speech therapy for lisps.
Clear speech can make conversations feel more natural and less effortful. When people don't need to repeat themselves as often, they can focus more on sharing their ideas and connecting with others.
The Four Types of Lisps
Lisps are categorized into four primary types based on tongue placement and airflow. Understanding the different types of lisps matters because each one changes the /s/ and /z/ sounds in its own way.
The fastest way to tell the four types of lisps apart is to listen carefully to the /s/ and observe where the tongue is placed. A clear "th" means an interdental lisp, and a muffled buzz with the tongue behind the teeth means a dentalized lisp. A slushy sound with air going sideways signals a lateral lisp, while a sound that is both slushy and muffled points to a palatal lisp.
Interdental Lisp (Frontal Lisp)
The interdental lisp, often called a frontal lisp, is the most common type of lisp. The tongue extends between the front teeth during /s/ and /z/ sounds, which makes them sound more like "th." For example, "sun" may sound like "thun," and "zoo" may sound like "thoo."
Unlike some other types of lisps, an interdental lisp is often part of typical speech development. Many young children use this pattern while learning speech sounds, and most stop doing so by about age 4 or 5.
Dentalized Lisp
A dentalized lisp occurs when the tongue rests against the back of the front teeth during /s/ and /z/ sounds. That contact disrupts the airflow, making the sound less sharp and more muffled than a typical /s/.
A dentalized lisp is also common during early speech development. Many children stop using this pattern as they gain better control of tongue placement and speech sound production.
Lateral Lisp
In a lateral lisp, the tongue is close to the correct position, but it sits too flat. Because the sides of the tongue are low, air escapes over the sides instead of flowing straight forward. Lateral lisps create a slushy sound due to air escaping sideways.
A lateral lisp is not part of typical speech development. It rarely fades on its own, so it usually calls for a professional evaluation.
Palatal Lisp
A palatal lisp occurs when the tongue moves too far back in the mouth during /s/ and /z/ sounds. The sound often lacks the sharp quality of a typical /s/ and may seem both muffled and slushy to the listener.
Palatal lisps are uncommon and are not considered part of typical speech development. Like lateral lisps, they usually require treatment from a speech-language pathologist rather than resolving on their own.
Can You Identify a Lisp at Home?
A simple listening check can provide clues about the type of lisp. Ask the person to say words such as "snake," "sun," and "bus." Listen for distorted /s/ sounds and watch whether the tongue moves between the front teeth.
A home screening can point you in the right direction, but it cannot confirm the diagnosis. A speech-language pathologist can identify the specific type of lisp, assess tongue placement patterns, and determine whether other factors are contributing to the speech difference.
What Causes a Lisp?
Lisps can develop for several reasons, including learned speech patterns, structural differences, or a combination of both. One of the most common causes is incorrect tongue placement during speech.
Often, the tongue has learned a movement pattern that changes how /s/ and /z/ sounds are produced. In some cases, a lisp begins as a speech error that becomes a long-standing speech habit.
Structural factors can also contribute to how a person speaks. A tongue-tie can limit tongue movement and cause the tongue to move into the wrong spot. Beyond a tongue tie, a cleft palate, dental alignment problems, and genetics can all influence how a lisp develops.
A tongue thrust is another common contributor. When the tongue pushes forward during speech or swallowing, it can reinforce the tongue positions associated with a lisp.
Hearing also affects speech development. A child who does not hear /s/ clearly may have more difficulty learning the sound accurately. Hearing differences can contribute to broader speech sound difficulties or, in some cases, a speech delay.
Less commonly, neurological conditions or muscular weakness can affect tongue movement and speech production. What causes a lisp? covers these factors in more detail, and How a Lisp Develops explains how these speech patterns can emerge and persist over time.
Speech Therapy for Lisps
Speech therapy can help correct a lisp at any age. Treatment begins with a speech evaluation to identify the type of lisp and any factors contributing to it. The goal is to improve tongue placement, speech clarity, and a person's ability to produce /s/, /z/, and related sounds accurately in everyday conversation.
Speech Therapy Techniques
A speech-language pathologist develops a treatment plan based on the specific type of lisp and the factors contributing to it. Those factors may include tongue thrust, dental alignment, hearing differences, or other speech sound difficulties. Therapy often focuses on helping the tongue reach the correct position as it rises toward the alveolar ridge during speech.
Mirrors, visual feedback, and targeted exercises can help reinforce accurate tongue placement and sound production. Practice usually progresses from individual sounds to words, sentences, and conversation. Different treatment approaches work best for different types of lisps, and the timeline varies from person to person.
Early intervention often leads to faster progress, which is why lateral and palatal lisps benefit from a prompt speech evaluation.
At-Home Practice
Home practice reinforces the skills learned during speech therapy. Short, consistent practice sessions are often more effective than occasional long drills. The goal is to build accurate speech habits that carry over into everyday communication.
Parents can support progress by encouraging practice between sessions and offering gentle reminders when appropriate. Our list of at-home speech tips includes simple activities that can help strengthen new speech patterns.
How to Fix a Lisp at Any Age
Learn how to fix a lisp at any age in this blog.
When to See a Speech-Language Pathologist
Consider consulting a speech-language pathologist if a lisp persists past age five. By that point, most children have moved beyond the developmental stage, so a persistent lisp is worth a closer look. Developmental lisps that continue beyond this age are less likely to resolve on their own.
Seek an evaluation sooner if you hear a lateral or palatal lisp at any age. These developmental lisps do not follow a typical path and rarely improve without help from a speech pathologist. A speech pathologist can confirm the type, check for a related speech sound disorder, and build a plan that fits your child's lisp or your own.
Preventing Lisps in Children
Not every lisp can be prevented, but some habits support typical speech development. Limiting prolonged thumb sucking and weaning children from pacifiers by about age three may help reduce the risk of changes to dental alignment and tongue posture. Those changes can sometimes contribute to speech sound difficulties.
Healthy breathing habits also matter. Chronic nasal congestion can encourage mouth breathing, which may affect resting tongue position and oral development over time. Addressing allergies and other causes of congestion early may support typical speech development.
Simple play activities can also increase awareness of the oral movements involved in speech. Drinking through straws and blowing bubbles encourages coordination of the lips, tongue, and airflow while keeping practice fun and engaging.
What We See Working With Clients
A six-year-old came to us with a classic interdental lisp. During show-and-tell at school, classmates sometimes asked him to repeat words like "sun," "snake," and "soup" because the /s/ sounded more like "th." When he looked in a mirror during sessions, he could see his tongue slipping between his front teeth each time he made the sound. After practicing a long "ssss" snake sound and learning to keep his tongue behind his teeth, he began using a clear /s/ in words, then sentences, and eventually in everyday conversation.
A teenager came in with a lateral lisp that gave her /s/ sounds a wet, slushy quality. She noticed it most when speaking in class and recording videos for school projects. At first, the distorted sound seemed normal to her, so we spent time comparing her production with a typical /s/ and helping her feel where the airflow should go. As she learned to direct air down the center of her tongue instead of the sides, the slushy quality faded, and her speech became noticeably clearer in conversation.
Frequently Asked Questions About Lisps
1. What is the most common type of lisp?
The interdental lisp, also called a frontal lisp, is the most common type of lisp. The tongue moves between the front teeth during /s/ and /z/ sounds, making them sound more like "th." It is also the type that children are most likely to outgrow as their speech develops.
2. Will a child outgrow a lisp on their own?
Some children outgrow frontal and dentalized lisps on their own. That often happens by age four or five. Lateral and palatal lisps differ in that they do not follow typical speech development and usually require a professional speech evaluation for correction.
3. Can you fix a lisp as an adult?
Yes. Adults can make significant progress in speech therapy, and it is never too late to work on speech clarity. Treatment focuses on retraining tongue placement and carrying those new speech patterns into everyday conversation. At-home practices can support progress in speech therapy.
4. How long does it take to correct a lisp?
Many people notice improvement within a few months, while others require longer-term support. Factors such as the type of lisp, age, contributing factors, and the amount of practice between sessions can all influence progress.
5. Can you fix a lisp at home without a speech-language therapist?
Home practice can be helpful, but it is usually most effective when guided by a speech-language pathologist. Personalized speech therapy sessions can identify tongue placement issues and provide a person with specific words to target during practice. Repeating an inaccurate speech pattern may reinforce the lisp rather than correct it.
How Connected Speech Pathology Can Help
At Connected Speech Pathology, our licensed speech-language pathologists work with children and adults to identify which type of lisp they have among the four types of lisps and correct it through personalized online therapy. Your speech-language pathologist starts with a careful evaluation, determines whether you are producing an interdental, dentalized, lateral, or palatal lisp, and develops a plan around your goals. Online speech therapy works well for many people, though the right fit depends on the individual.
Parents who notice a lisp in their child's speech and adults seeking clearer communication can both benefit from speech therapy. A speech-language pathologist meets each person at their current skill level and develops a plan based on their goals.
Summary
A lisp changes the /s/ and /z/ sounds through differences in tongue placement and airflow. The four main patterns are interdental, dentalized, lateral, and palatal. You can often identify the type you hear by the sound, whether it is a "th," a muffled buzz, or a slushy hiss, and by watching where the tongue sits relative to the teeth.
Frontal and dentalized lisps are common in early childhood and frequently resolve on their own, while lateral and palatal lisps usually need a speech-language pathologist. With the right treatment methods and consistent practice, the different types of lisps respond well at any age, helping both children and adults move toward clearer, more confident speech.
About the Author
Allison Geller, M.A., CCC-SLP, is a communication coach, speech-language pathologist, and founder of Connected Speech Pathology, an international online practice providing professional communication coaching and speech therapy for children, teens, and adults. With more than two decades of experience, she has worked in medical and educational settings and published research on aphasia. Today, she leads a team of specialists who help clients improve their skills in public speaking, vocal presence, accent clarity, articulation, language, fluency, and interpersonal communication.
