Types of Lisps: Definitions, Causes & Key Differences

Have you ever noticed how some people say “thith” instead of “this” or “tho” instead of “so”? That’s a lisp, one of the most common speech differences people experience.

While many folks think all lisps sound the same, there are several distinct types, each with its own causes and characteristics.

Understanding these differences matters more than most people realize. The truth is, lisps aren’t just one thing.

Some occur due to tongue placement, others due to dental issues, and some develop for entirely different reasons. Each type requires a different approach and yields different outcomes.

This guide breaks down the main types of lisps, explains what causes them, and highlights the key differences everyone should know about.

What Is a Lisp?

A lisp is an everyday speech sound disorder that affects how a person pronounces certain consonant sounds, especially the /s/ and /z/ sounds.

People with a lisp may push their tongue too far forward or sideways when speaking, causing words to sound unclear or “slushy.”

This condition can make everyday communication somewhat challenging and may lead to feelings of self-consciousness, particularly for children. Lisps vary in type and severity, but they’re generally treatable with proper speech therapy and practice.

Understanding what a lisp is helps parents, teachers, and caregivers support children or adults who have one, encouraging clear speech and boosting confidence over time.

What Causes a Lisp?

A lisp can develop for various reasons, and understanding these helps in treating it effectively. Children and adults alike may develop a lisp due to physical, developmental, or habitual factors.

• Anatomical reasons: Problems like a tongue tie, weak tongue muscles, or poor tongue placement can cause a lisp.
• Teeth alignment: Issues like gaps between teeth, an overbite, or crowded teeth can disrupt proper speech sound formation.
• Developmental phase: It’s quite normal for young children to have a slight lisp as they learn to talk, but it should fade by age five.
• Learned behaviors: Some lisps originate from adopting incorrect speech patterns that become ingrained habits over time.
• Neurological or muscular issues: Rarely, muscle weakness or neurological conditions can make it harder to control tongue movements.

Recognizing these causes can help parents and speech therapists guide proper treatment and support clear speech.

Understanding The 4 Main Types of Lisps

Speech experts commonly categorize lisps into four main types based on how the tongue and airflow affect sounds. Knowing these types helps parents and therapists choose the right approach for correction.

1. Interdental Lisp

An interdental lisp happens when the tongue pushes forward between the front teeth while speaking. This makes ‘s’ and ‘z’ sound more like ‘th’, so words can sound softer or unclear. It’s very common in young children and often goes away naturally as they grow.

• Tongue Between Teeth: The tongue slips between the top and bottom front teeth during sounds.
• ‘Th’ Sound Substitution: ‘S’ and ‘z’ are often replaced with a ‘th’, like saying ‘thun’ for ‘sun’.
• Common Causes: Usually due to tongue thrust habits or gaps in front teeth; often a normal stage in early speech.

2. Dentalized Lisp

A dentalized lisp occurs when the tongue pushes firmly against the back of the front teeth but doesn’t poke out. This causes slight distortion of ‘s’ and ‘z’ without changing them into ‘th’. It may make speech sound muffled or less sharp.

• Tongue Touches Teeth: The tongue touches or presses into the back of the front teeth.
• Mild Distortion: Sounds stay as ‘s’ and ‘z’ but lose clarity.
• Possible Causes: Often linked to habitual tongue placement, dental alignment, or learned patterns.

3. Lateral Lisp

A lateral lisp means that instead of air flowing forward over the tongue, it escapes out the sides. This creates a distinctive wet, ‘slushy’ sound, which is easy to hear. Unlike other lisps, a lateral lisp rarely resolves on its own and usually needs speech therapy.

• Side Airflow: Air leaks over the sides of the tongue instead of down the middle.
• ‘Slushy’ Sound: Speech sounds wet or messy, especially for ‘s’, ‘z’, ‘sh’, and ‘ch’.
• Root Causes: Can develop from mislearned tongue movement, weak tongue muscles, or poor coordination.

4. Palatal Lisp

A palatal lisp happens when the tongue contacts the soft part of the roof of the mouth further back than usual. This placement muffles sounds like ‘s’ and ‘sh’, making them unclear. It’s less common and may need treatment if it persists.

• Tongue Touches Palate: The tongue hits the soft palate (back roof of mouth) instead of the ridge behind the teeth.
• Muffled Speech: Sounds don’t come out crisp; they’re softened or ‘backed’.
• Likely Causes: Sometimes caused by habits, unusual tongue placement, or structural issues needing a speech therapist’s help.

Key Differences Between Lisp Types

Lisps are not all the same; speech experts categorize them into four main types to better understand and treat them. Each type has unique tongue placement and sound features that affect how words are spoken.

Type of Lisp	Where the Tongue Is Placed	How It Sounds	Common Example
Interdental Lisp	The tongue pushes out between the front teeth	Sounds like “th” instead of clear/s/s/ or /z/	Saying “sun” as “thun”
Dentalized Lisp	Tongue presses against the back of the front teeth	Airflow is blocked, causing a muffled or distorted sound	“Soap” sounds unclear or heavy
Lateral Lisp	The tongue allows air to escape over the sides	Produces a wet, slushy, or “slurpy” sound	“Slide” sounds messy or bubbly
Palatal Lisp	Tongue touches the palate (roof of the mouth) further back than normal	Creates an unusual hissing or harsh sound	“Silly” has an exaggerated hiss

Understanding these differences makes it easier for parents and therapists to identify the type of lisp and choose the appropriate treatment steps. A targeted approach helps children and adults achieve clearer speech with greater confidence.

When Should You Seek Help for a Lisp?

Most young children have slight lisps while learning to speak, and this is usually normal until around age four or five.

If a lisp persists beyond this age, especially a lateral or palatal lisp, it’s wise to get a speech-language evaluation. Seek help if your child feels frustrated, avoids talking, or if the lisp affects understanding.

Adults with a lingering lisp can benefit significantly from speech therapy, too; it’s never too late to improve clarity and confidence.

Remember, lisps are common and nothing to be ashamed of. Early support can make speech more straightforward and boost self-esteem.

If in doubt, consult a certified speech-language pathologist to see if therapy would help your child or you speak your best.

Treatment Options for Lisp

Treating a lisp often involves working with a speech-language pathologist who tailors exercises to strengthen correct tongue placement and airflow. With time, practice, and patience, most people see significant improvement.

• Speech Therapy Sessions: A certified therapist guides structured lessons to correct tongue position and sound production.
• Articulation Exercises: Repeated practice of sounds and words helps retrain the tongue’s movement during speech.
• Home Practice: Simple daily activities at home, such as reading aloud and playing word games, accelerate progress.
• Early Intervention: Starting therapy early can facilitate corrections and prevent the development of lasting speech habits.

Stay positive and consistent, with professional help and practice, a lisp can be successfully treated at any age.

Conclusion

Every person’s speech trip looks different, and that’s perfectly normal. Understanding the various types of lisps helps parents, teachers, and individuals recognize when professional support might be helpful.

From interdental lisps where the tongue slips between teeth, to lateral lisps that create that distinctive sound, each type has its own characteristics and treatment approaches.

The good news? Most lisps can be improved with the proper guidance and support. Speech therapy techniques, consistent practice, and patience make a real difference.

Remember, having a lisp doesn’t define anyone’s intelligence or worth. Parents and individuals dealing with lisps shouldn’t feel alone in this process. Professional help is available, and progress happens one step at a time.

What’s your experience with speech therapy? Drop a comment below or check out our other articles on speech development!