A lisp is a common speech sound disorder involving the misarticulation of sibilant sounds, primarily “s” and “z.” This difficulty stems from incorrect tongue positioning or movement during speech. While some lisps are typical developmental phases for young children, the lateral lisp is a specific articulation error that is never age-appropriate and requires professional intervention. A lateral lisp significantly impacts speech clarity and intelligibility.
The Mechanics of a Lateral Lisp
A lateral lisp is defined by a physical production error that redirects airflow during speech. For a correct “s” or “z” sound, the air stream must be channeled narrowly down the center of the tongue and out the front of the mouth. In a lateral lisp, the tongue fails to create this central groove, allowing air to escape over the sides instead. This lateral air escape occurs because the tongue’s sides are lowered, rather than sealed against the back molars, which is the proper placement.
This misdirection of air produces an acoustic quality often described as “slushy,” “wet,” or “sizzly.” The distortion occurs because the air is not focused enough to create the clear, high-frequency friction sound of a correct sibilant. The lateral lisp can also affect other sounds requiring a focused air stream, such as “sh,” “ch,” “j,” and “zh.” This incorrect sound production is a motor-based error involving the physical movement and coordination of the speech articulators.
Factors Contributing to Lateral Lisp Development
A lateral lisp is often linked to a combination of learned habits and underlying physical factors. A common cause is an incorrect motor pattern established during speech development that was never corrected. This learned habit of improper tongue placement becomes the default setting for producing sibilant sounds.
Physical and Structural Influences
Muscle factors, such as weakness or poor coordination in the oral musculature, can prevent the tongue from achieving the precise position needed to seal the sides of the mouth. The resting posture of the tongue, if habitually too low or to the side, reinforces the incorrect speech pattern. Structural issues, though less common, may also contribute, including a high or narrow palate, or misaligned teeth that interfere with correct tongue placement. Habits like prolonged thumb-sucking or pacifier use can influence oral structure development, making the correct tongue-to-palate relationship more challenging.
Professional Assessment and Correction
Since a lateral lisp is not a developmental error that a person typically outgrows, professional assessment by a Speech-Language Pathologist (SLP) is recommended. The SLP conducts a comprehensive evaluation, identifying the specific sounds affected and assessing oral-motor function. This assessment includes the strength, mobility, and coordination of the tongue, which guides the development of a tailored treatment plan.
Therapy focuses on training the tongue muscles to redirect airflow from the sides back to the center of the mouth. SLPs use specific techniques, often involving tactile and visual cues, to help the individual feel and see the correct tongue position. Techniques include phonetic shaping, where the target sound is gradually developed from a sound the person already produces correctly, such as “n” or “t.” The primary goal is to establish a new, correct motor pattern for sibilant sound production.
Consistent practice is an important component of therapy, as the individual must replace a deeply ingrained habit with a new, coordinated movement. The SLP works on establishing the correct sound in isolation, then progresses to syllables, words, and eventually conversational speech. Dedicated intervention allows individuals to successfully correct their lateral lisp and achieve clear, focused speech production.