Lisps are characterized by misarticulation of sibilant consonants, most commonly the alveolar fricatives /s/ and /z/. In an interdental lisp, the tongue protrudes between the front teeth, causing /s, z/ to sound like /θ, ð/ (as in “thun” for “sun”). In a lateral lisp, airflow escapes over the sides of the tongue, producing a slushy or “wet” quality to the sibilant. Lisps are a subset of functional speech sound disorders (historically termed sigmatism) and can persist into later childhood or adulthood if not corrected. Speech therapy for lisps focuses on training correct tongue positioning and airflow for clear sibilant production.
John Van Borsel, Sigrid Van Rentergem, and Leen Verhaeghe. “The Prevalence of Lisping in Young Adults.” Journal of Communication Disorders 40, no. 6 (2007).
Caroline Bowen. “Lisping – When /s/ and /z/ Are Hard to Say.” Speech-Language-Therapy.com, (2011).
