Functional Speech Disorders INDEX

Development of /s/ and /z/
Typical speech development in children is a gradual process and many children go through a  NORMAL stage of producing /s/ and /z/ with the tongue between the teeth. This is called interdental production, or an interdental /s/ or /z/. Interdental esses and zeds (zees) cause words like sick to be pronounced as thick, and zoo to be pronounced as thoo. 

Other children do not produce the /s/ and /z/ sounds with the tongue between the teeth, but rather with the tongue touching the teeth. This is called dentalised production or dentalised /s/ and /z/. When they do this, their esses and zeds (zees) may sound muffled, or indistinct or even have a bit of a whistling sound associated with them. 

Follow this link this link to find out more about typical speech acquisition.

Normal production of /s/ and /z/
In linguistic description, this is one way of delineating the normal production of /s/ and /z/.

[s] VOICELESS ALVEOLAR FRICATIVE
[+Consonant -Vowel +Alveolar -Stop +Fricative -Voiced]

[z] VOICED ALVEOLAR FRICATIVE
[+Consonant -Vowel +Alveolar -Stop +Fricative +Voiced]

Atypical production of /s/ and /z/

What is a lateral ess?
'Lateral s', 'lateralized s' and 'lateral lisp' are different names for one particular type of functional speech disorder. 

The tongue position for a lateral lisp is very close to the normal position for /l/ and the sound is made with the air-flow directed over the sides of the tongue. Because of the way it sounds, this sort of lisp is sometimes referred to as a slushy ess or a slushy lisp. A lateral lisp often sounds wet or spitty.

Usually individuals who produce /s/ with lateral air escape also produce /z/ that way too. 

Some individuals lateralize both the affricates (ch and j) and the fricatives /s/, /z/, 'sh' and 'zh'.

What is a palatal ess?
'Palatal s' and 'palatal lisp' are different names for one particular type of functional speech disorder.

Palatal lisps are not found in typical speech development. Here, the mid-section of the tongue comes in contact with the soft palate, quite far back. If you try to produce a /ç/ - or a 'h' closely followed by a 'y', and prolong it, you more or less have the sound. 

FRONTAL LISPS ARE FOUND IN TYPICAL DEVELOPMENT
Interdental and dentalised production of /s/ and /z/ are both considered to be types of frontal lisp, and both are seen as a normal stage in speech development.

LATERAL LISPS ARE NOT FOUND IN TYPICAL DEVELOPMENT
Unlike interdental and dentalised lisps, lateral lisps are not characteristic of normal development. An SLP assessment is indicated for anyone with a lateral lisp. 

PALATAL LISPS ARE NOT FOUND IN TYPICAL DEVELOPMENT
Unlike interdental and dentalised lisps, palatal lisps are not characteristic of normal development. An SLP assessment is indicated for anyone with a palatal lisp. 

Page updated 21 May 2009

http://www.speech-language-therapy.com/fsd-norms.htm