Lisp: Types, Causes, and Evidence-Based Therapy That Helps Canadians Communicate Clearly

When people talk about a “lisp,” they usually mean trouble producing the sounds /s/ and /z/ clearly—often with a tongue position or airflow pattern that makes speech sound slushy or muffled. A lisp is common in childhood and can persist into adulthood without support. This article explains what a lisp is, how it’s assessed and treated, and practical strategies Canadian families can use to help children and adults speak more clearly.

What is a lisp?

A lisp is a speech sound error that affects how a person produces sibilant sounds, most often /s/ and /z/. Instead of the crisp, central stream of air between the tongue and the alveolar ridge (the bumpy area just behind your top front teeth), the airflow may escape forward through the teeth or sideways along the cheeks. The result is a sound that can be perceived as “slushy,” “wet,” or distorted.

Lisps can be developmental (common as kids learn speech sounds) or can persist if habits, structure, or sensory-motor patterns keep the incorrect production in place. Speech-Language Pathologists (SLPs) are trained to pinpoint the specific pattern and guide targeted therapy.

Common types of lisp

Not all lisps are the same. Knowing the type helps determine the most effective treatment plan.

Interdental lisp

The tongue pokes between the teeth during /s/ and /z/, creating a sound that can resemble “th” (as in “think”). This is often what people picture when they hear “lisp.”

Dentalized lisp

The tongue presses against the back of the teeth for /s/ and /z/, causing air to diffuse over the teeth and blurring the sound’s clarity.

Lateral lisp

Air escapes over one or both sides of the tongue instead of down the centre, producing a distinctly “wet” or “slushy” quality. Lateral lisps typically require direct intervention; they rarely resolve on their own.

Palatal lisp

The tongue is placed too far back toward the hard palate. The sound may be distorted or sound like a different phoneme entirely.

Is a lisp normal in childhood?

Children master speech sounds at different ages. It is common for younger children to be working on /s/ and /z/ in early school years. For a clear picture of typical timelines, see Understanding Speech Sound Development by Age.

Even when a lisp is part of typical development, families often choose support to promote clearer speech sooner. If a lisp persists, affects a child’s confidence, or interferes with reading/spelling (for example, confusing “s” and “th”), a Speech-Language Pathologist can help.

Causes and risk factors

A lisp often reflects a learned speech pattern, but several factors can contribute. A thorough assessment examines structure, function, and habits.

Oral structures and dentition

Missing teeth, bite alignment differences (e.g., open bite), high or narrow palate, or tongue posture habits can affect airflow and sound quality. Dental changes (braces, extractions, dentures) can temporarily alter speech patterns in teens and adults.

Hearing and sensory factors

Reduced hearing or auditory processing differences can make it harder to self-monitor the fine details of sounds. Sensory factors (e.g., reduced tongue awareness) can also play a role.

Motor planning and neuromotor factors

While a lisp is not the same as a motor planning disorder, some children have broader speech motor coordination needs. If you suspect motor planning challenges, explore childhood apraxia of speech to understand how SLPs assess and treat motor-based issues.

How Speech-Language Pathologists assess a lisp

An SLP uses detailed observation and standardized tools to identify the exact error pattern. Assessment typically includes:

• Oral mechanism exam to check tongue, jaw, palate, and dental status.
• Sound inventory to see which sounds and word positions are affected.
• Stimulability testing—can the person produce a clearer sound with coaching?
• Speech sampling in conversation for real-world impact.
• Functional goals discussion (school, work, social situations).

This guides a tailored therapy plan, which is more efficient than generic drills. For a broader overview of speech differences and support, see our plain-language guide to speech impediments.

Evidence-based therapy that works

With focused practice, most people can learn a crisp, central /s/ and /z/. Therapy is typically short-term and highly practical. Our detailed resource on how to get rid of a lisp outlines step-by-step strategies; the essentials are summarized below.

Phonetic placement and tactile cues

Phonetic placement teaches exactly where to put the tongue and how to shape the lips. Tactile cues (e.g., a tongue depressor for feedback) help learners feel the correct position. For /s/ and /z/:

• Lightly touch the tip of the tongue to the alveolar ridge, not the teeth.
• Keep the sides of the tongue lifted to form a “groove” down the centre.
• Smile gently; avoid rounding like “sh.”
• Maintain teeth close together without clenching.

Short, focused bursts of practice (1–3 minutes, several times daily) are more effective than long sessions.

Airflow and frication control

The “hiss” of /s/ comes from controlled, central airflow. Useful techniques include:

• Straw test: Place a straw in the centre of the lips and aim airflow through it while making /s/. This encourages midline air.
• Paper test: Hold a small paper strip in front of the lips; aim to make it flutter straight forward, not sideways.
• Quiet-loud contrast: Practise whispering /s/ softly, then gradually increase intensity while keeping a clean central stream.

Sound shaping and generalization

SLPs often shape the sound from an easier target (e.g., start with /t/, which is crisp and alveolar, then “stretch” the release into /ts/ and finally /s/). Once clear /s/ is established in isolation, practise:

• Syllables: “sa,” “si,” “so,” “su.”
• Words: Start with simple words (“sun,” “bus,” “ice”), then move to /s/ blends (“sky,” “stay,” “spin”).
• Sentences and conversation: Read aloud, role-play, and everyday chats.

Generalization is the goal—using the new sound consistently across contexts. Functional practice (class presentations, job interviews, phone calls) helps the skill stick.

Practical at-home strategies

Parents and caregivers make a big difference by weaving practice into daily routines. Try:

• Mirror work: Practise in front of a mirror to monitor tongue and lip position.
• One-minute drills: Keep short word lists on the fridge; do a quick set before school.
• Game-based practice: Use board games; earn a turn after five /s/ words.
• Reading routines: Highlight words with /s/ and /z/ during shared reading.
• Low-pressure feedback: Gently prompt a “clean centre hiss,” then praise the effort.

For more ideas, explore practical speech therapy tips for kids you can use at home.

Lisp in bilingual or multilingual families

Language diversity is part of Canadian life. Statistics Canada tracks multilingual households across the country, and many children learn sounds across two or more languages. A lisp is a speech sound production pattern, not a language issue, but sound inventories and phonotactics vary across languages.

An SLP familiar with bilingual development will consider which sounds exist in your languages and how transfer effects might appear. Therapy can be planned to support clarity across languages, focusing on shared sounds and contexts that matter most at home and school.

Lisp in teens and adults

Some teens and adults seek support to improve clarity for social, academic, or professional reasons. Others notice changes after dental work or orthodontic treatment. Therapy is effective at any age with targeted coaching and practice.

Adults benefit from real-world tasks: practising presentations, mock interviews, or customer service scripts. Progress is often faster because adults can self-monitor precisely and apply feedback in structured practice.

Navigating care in Canada

SLPs provide assessment and therapy in schools, hospitals, community clinics, and private practice. Learn more about speech therapy in Canada, including evidence-based support options. If you are searching for a provider, see our guidance on how to find quality speech therapy that fits your life.

For broader information about Canada’s health system and services, visit Health Canada or explore health and social resources through the Government of Canada. These sites outline national frameworks and can help you navigate provincial and territorial services.

Myths and misconceptions about lisps

• “Kids will just grow out of it.” Some do, but lateral and palatal lisps rarely resolve without targeted intervention.
• “A lisp is just cosmetic.” A lisp can affect intelligibility and confidence. Therapy improves clarity and self-assurance.
• “Practising tongue twisters fixes it.” Tongue twisters can reinforce the wrong pattern. Correct placement and airflow come first, then speed.
• “It’s caused by laziness.” Lisps are learned motor patterns influenced by structure and sensory feedback—not motivation.

Communication disorders are a public health priority. The World Health Organization underscores the importance of early identification and evidence-based rehabilitation to reduce long-term impacts on education, employment, and wellbeing.

Conclusion

A lisp is a specific, fixable speech pattern affecting the clarity of /s/ and /z/. With accurate assessment, clear instruction on tongue placement and airflow, and steady practice, children and adults can achieve a crisp, confident sound. Canadian families have access to practical resources and qualified SLPs who tailor therapy to each person’s goals and everyday life.