A lisp (OE wlisp, stammering) is a speech impediment, historically also known as sigmatism. Stereotypically, people with a lisp are unable to pronounce sibilants (like the sound [s]), and replace them with interdentals (like the sound [θ]), though there are actually several kinds of lisp. The result is that the speech is unclear.
"Interdental" lisping is produced when the tip of the tongue protrudes between the front teeth and "dentalised" lisping is produced when the tip of the tongue just touches the front teeth.
The "lateral" lisp, where the /s/ and /z/ sounds are produced with air escaping over the sides of the tongue, is also called 'slushy ess' or a 'slushy lisp' due to the wet, spitty sound. The symbols for these lateralized sounds are in the Extended International Phonetic Alphabet for speech disorders, [ʪ] and [ʫ]. Notably the former mayor of New York, Rudolph Giuliani, has this type of lisp.
Finally, there is the "palatal lisp," where the speaker attempts to make the sounds with the tongue in contact with the palate.
The cause of a lisp can vary. In some instances, the cause is physiological, and the patient has some sort of deformity or medical condition which causes a lisp. For example, a child with swollen adenoids may tend to lisp, as will people who have recurring stuffy noses. Also, a lisp can be formed when the tongue is bruised or swollen.
Treating lisps in children usually involves speech therapy treatments and is generally successful. Speech therapy sessions include a wide variety of activities and speech drills, though what specifically happens in any given session will depend upon many variables. The length of the therapy session (usually between a half hour and one hour), the location of the therapy session (whether at home, school or a private facility), the age of the child involved, whether the therapy session is private or involves a group, and the type of lisp that is being treated will all affect the content of these sessions.
One popular method of correcting articulation or lisp disorders is to isolate sounds and work on correcting the sound in isolation. The basic sound, or phoneme, is selected as a target for treatment. Typically the position of the sound within a word is considered and targeted. The sound appears in the beginning of the word, middle, or end of the word (initial, medial, or final).
Take for example, correction of an “S” sound (lisp). Most likely, a speech-language pathologist (SLP) would employ exercises to work on “Sssssss.” Starting practice words would most likely consist of “S-initial” words such as “say, sun, soap, sip, sick, said, sail.” According to this protocol, the SLP slowly increases the complexity of tasks (context of pronunciations) as the production of the sound improves. Examples of increased complexity could include saying words in phrases and sentences, saying longer multi-syllabic words, or increasing the tempo of pronunciation.
