A lisp is visible as unusual tongue placement during speech, most often when making “s” and “z” sounds. Depending on the type, you might see the tongue poking out between the teeth, pressing flat against the front teeth, or sitting too low on the sides. The sound that comes out is equally distinctive: a “s” that sounds more like “th,” or a wet, slushy quality that doesn’t match normal speech patterns.
The Four Types and How They Look
Not all lisps look the same. There are four recognized types, each with a different tongue position and a different resulting sound.
Frontal (Interdental) Lisp
This is the most common and most recognizable type. The tongue slides forward between the upper and lower front teeth when making “s” or “z” sounds. You can often see the tip of the tongue poking out between the teeth mid-word. The result is that “s” sounds like “th,” so “sun” becomes something closer to “thun.” This is the lisp most people picture when they hear the word.
Lateral Lisp
A lateral lisp is harder to spot visually but easy to hear. The tongue is almost in the correct position, but its sides sit too low in the mouth. Instead of air flowing in a narrow stream down the center of the tongue (which produces a clean “s”), air escapes over the sides. The sound that comes out is wet or slushy, sometimes described as a “sloshy s.” You may notice the jaw shifting slightly or the cheeks puffing as air moves laterally. Weak mouth muscles and teeth misalignment can contribute to this pattern.
Dentalized Lisp
This one looks similar to a frontal lisp but with a subtle difference. The tongue doesn’t push all the way between the teeth. Instead, it presses firmly against the back of the upper front teeth. The tongue tip stays behind the teeth rather than protruding, so it’s less visible from the outside. The sound is muffled or dull compared to a crisp “s,” but it doesn’t fully turn into a “th” the way a frontal lisp does.
Palatal Lisp
The rarest type. Here, the middle of the tongue contacts the roof of the mouth too far back when attempting “s” or “z” sounds. You won’t see much from the outside since the action happens deep in the mouth, but the sound is noticeably off. It can come across as a “hy” or soft “sh” quality because the tongue is bunched up against the hard palate rather than channeling air through a narrow groove near the front.
What a Lisp Sounds Like in Conversation
The affected sounds are almost always “s,” “z,” “sh,” and sometimes “j” and “ch.” These sounds all require precise tongue placement and a controlled stream of air, which is exactly what a lisp disrupts. A person with a frontal lisp saying “I saw six zebras” might produce something like “I thaw thix theebras.” A lateral lisp on the same sentence would sound more like the “s” and “z” sounds are waterlogged.
Most lisps only affect these specific sounds. The rest of a person’s speech is typically clear and fluent, which is one way lisps differ from broader speech disorders. The inconsistency can actually make the lisp more noticeable, because the listener hears normal speech punctuated by distorted sounds.
Tongue Thrust and Its Connection
Many children with a lisp also have a pattern called tongue thrust, where the tongue pushes forward against or between the teeth not just during speech but also when swallowing and even at rest. Signs of tongue thrust include the tongue visibly protruding during swallowing, frequent mouth breathing, and accidentally biting the tongue or cheek. A child with tongue thrust might pronounce “say” as “thay” because the forward tongue position has become their default. This habit reinforces the lisp by keeping the tongue in the wrong resting position throughout the day, not just during speech.
When a Lisp Is Normal and When It’s Not
Young children commonly lisp, and it’s not always a concern. The “s” sound is one of the later sounds children master. Research published in the American Journal of Speech-Language Pathology found that children typically acquire the “s” sound by around 51 months (just over 4 years old), while “z” comes in around 57 months. The “th” sound, which requires similar tongue-tip control, isn’t reliably produced until age 6 or 7. So a 3-year-old who says “thun” instead of “sun” is within the normal developmental window.
Frontal and dentalized lisps are considered developmental, meaning most children outgrow them naturally as their oral muscles strengthen and their coordination improves. Lateral and palatal lisps are different. These are not part of typical development and rarely resolve on their own. If a child produces that wet, slushy “s” sound at any age, speech therapy is generally recommended rather than waiting it out.
By first grade, roughly 5% of children have noticeable speech disorders of some kind. Speech sound disorders, which include lisps, affect about 8 to 9% of young children overall. Many of these resolve with age or therapy, but a lisp that persists past age 7 or 8 is unlikely to disappear without intervention.
What to Watch for in Children and Adults
If you’re trying to determine whether someone has a lisp, focus on words with “s” and “z” sounds. Ask them to say a sentence like “Sally sees six snakes” and watch their mouth. With a frontal lisp, you’ll see the tongue tip appear between the teeth on every “s.” With a dentalized lisp, the tongue stays behind the teeth but pushes forward against them. A lateral lisp won’t show you much visually, but the sound will have a distinct slushy or spitty quality.
In adults, a lisp usually looks and sounds the same as it does in children, just more practiced. Adults with lisps have often developed subtle compensations, like speaking quickly through problem words or avoiding certain phrases. The tongue position itself, though, remains the same: too far forward, too flat against the teeth, or too low on the sides. Speech therapy works for adults as well as children, though it typically takes longer because the motor patterns are more deeply established.