If you’ve ever heard someone pronounce “sun” as “thun” or “slippery” as “shlippery,” you’ve likely heard a lisp. Lisps are among the most common speech sound errors children experience, and while they’re normal at certain ages, some persist and require therapy.

As a speech-language pathologist (SLP), understanding the different types of lisps is key to providing effective, individualized treatment. This guide explains the four main types of lisps, what causes them, and how speech therapy helps children and adults speak clearly and confidently.

What Is a Lisp?

A lisp is a speech pattern that affects how someone produces the /s/ and /z/ sounds. Instead of air flowing cleanly down the middle of the tongue, it escapes in the wrong direction—forward, sideways, or toward the palate—causing the sound to change.

Lisps are not caused by laziness or low intelligence; they simply reflect a learned tongue placement pattern that can be corrected with awareness and practice.

The Four Main Types of Lisps

Each type of lisp has a distinct tongue placement and sound quality.

1. Frontal Lisp (Interdental Lisp)

Description:
This is the most common type of lisp. The tongue protrudes between the front teeth when saying /s/ or /z/, making them sound like “th.”

Example:
“Sun” → “thun”
“Zebra” → “thebra”

What It Sounds Like:
Soft and airy, often mistaken for a “th” substitution.

Causes:

• Typical developmental pattern for children under age 4½.

• Prolonged pacifier or thumb-sucking habits.

• Learned tongue-forward posture during speech.

Speech Therapy Approach:

• Teach tongue retraction: keeping the tip just behind the top teeth, not between them.

• Use mirrors for visual feedback.

• Contrast minimal pairs (e.g., “sip” vs. “thip”) to build auditory awareness.

• Practice in isolation, syllables, and words, then move to phrases and conversation.

2. Lateral Lisp

Description:
Air escapes from the sides of the tongue instead of the center, creating a “slushy” or “wet” sound.

Example:
“See” → “shlee”
“Soup” → “shloop”

What It Sounds Like:
Watery, distorted, or similar to a “sh” sound—but with air escaping sideways.

Causes:

• Incorrect tongue placement along the sides.

• Lack of tongue stability when producing /s/ and /z/.

• Oral motor habits or structural variations in the mouth.

Speech Therapy Approach:

• Teach central airflow by having the child blow air straight ahead (using straws or feathers).

• Use auditory feedback tools or speech apps to help the child hear the difference.

• Practice tongue tip placement behind the teeth with strong airflow through the middle.

• Build from isolated sounds to longer words and sentences.

3. Palatal Lisp

Description:
The tongue touches or gets too close to the soft palate (back of the mouth) when making /s/ and /z/, producing a muffled “sh” sound.

Example:
“See” → “shee”
“Soup” → “shoop”

What It Sounds Like:
Soft, distorted, almost like a whispery “sh.”

Causes:

• The tongue is pulled too far back in the mouth.

• Learned articulation error or imitation of unclear models.

• Occasional oral-motor or sensory differences.

Speech Therapy Approach:

• Teach forward tongue placement using mirrors and visual cues.

• Emphasize the difference between “s” (front) and “sh” (back).

• Use tactile feedback—like placing a straw in the middle of the lips—to guide airflow.

• Practice accurate /s/ and /z/ productions in short bursts, then extend gradually.

4. Dentalized Lisp

Description:
The tongue pushes against the front teeth instead of staying just behind them, distorting the /s/ and /z/ sounds.

Example:
“See” → sounds muffled, with air hitting the teeth instead of flowing cleanly.

What It Sounds Like:
A dull or buzzy “s” without a clear hiss.

Causes:

• Learned placement error.

• Jaw tension or forward tongue posture.

• Prolonged oral habits (e.g., bottle or pacifier use).

Speech Therapy Approach:

• Teach tongue placement just behind the teeth (not touching).

• Use mirrors and tongue depressors for positioning awareness.

• Provide auditory contrast between correct and dentalized /s/ sounds.

• Reinforce correct posture in natural conversation.

When Is a Lisp Normal—and When Is It Not?

Lisps are common during early speech development, but most children outgrow them by around age 4½ to 5.

You may want to consult an SLP if:

• Your child is over 5 and still lisps.

• The lisp affects multiple sounds or impacts confidence.

• Teachers or unfamiliar listeners have trouble understanding your child.

• The lisp has not improved with modeling or time.

An SLP can evaluate the type of lisp, identify underlying causes, and create a personalized therapy plan.

Speech Therapy Techniques for Lisps

Speech therapy for lisps focuses on awareness, correct placement, and consistent practice.

Common methods include:

• Mirror work: Watching the tongue’s position.

• Auditory feedback: Listening to correct vs. incorrect sounds.

• Minimal pairs: Highlighting meaning changes (“sip” vs. “ship”).

• Straw or airflow training: Directing air straight through the mouth.

• Step-by-step practice: From isolated sounds → syllables → words → sentences → conversation.

Therapy is play-based for young children and functional for older students or adults.

How Long Does It Take to Fix a Lisp?

The timeline depends on the child’s age, type of lisp, and consistency of practice. Some children show improvement in a few months, while others need a year or more of structured therapy and home practice.

The most important factor? Daily repetition and positive feedback.

FAQs

Is a lisp harmful?
A lisp doesn’t harm physical speech mechanisms, but it can affect clarity and self-confidence if not treated.

Can adults correct a lisp?
Yes. Adults can successfully eliminate lisps through articulation therapy—progress often comes quickly with awareness and motivation.

Are lisps caused by dental issues?
Sometimes dental alignment or bite patterns can influence tongue placement, but most lisps are functional (learned habits), not structural.