Moses said to the LORD, "O Lord, I have never been eloquent, neither in the past nor since you have spoken to your servant. I am slow of speech and tongue."
-- Exodus 4:10
A lisp is a functional speech disorder. That is to say, it's a problem that a person may have with pronouncing a given sound. A wide variety of functional speech disorders exist, but a "lisp" specifically refers to a difficulty in pronouncing the letters S and Z.
Speech-language pathologists recognize four kinds of lisps: interdental (or "frontal"), dentalized, lateral, and palatal lisps.
Lisps that can be a part of "normal" speech development
Interdental and dentalized lisps are frequently found in children who have not yet perfected the art of pronouncing esses. Though not all children lisp, many do until the age of four or so, and then naturally grow out of it. For this reason, lisping is often associated with kids, and in our culture it's often seen as cute or endearing. Many children are surprised and confused when their parents -- who indulged them, and perhaps even encouraged them to lisp for years -- suddenly declare that it's time for them to "talk properly."
The children who go through a phase of lisping as they learn to talk usually grow out of it on their own. The two sorts of lisps below are nothing for a parent to worry about unless a child continues to do it past the age of five. Even then, it's not helpful to bully the child or to belittle her manner of speaking. It's best to talk to a professional speech pathologist and see what they recommend as a course of action.
- An interdental (literally, "between the teeth") lisp occurs when a child puts her tongue between her teeth whenever she tries to make the /s/ sound. What she gets instead is a voiceless /th/ sound, like in the word "thing". (Remember the way Sylvester the Cat would holler "Thufferin' Thuccotash!"?) When the child tries to pronounce /z/, what she gets instead is a voiced /th/ sound, like in the word "there."
- A dentalized lisp occurs when a child presses his tongue against the back of his front teeth while trying to say /s/. The result isn't as noticeable as an interdental lisp, but it does make the sound seem "muffled."
Incidentally, many children "dentalize" a lot of sounds, including /r/ and /l/ as well as /s/ and /z/. It is normal for a toddler to push many of her words to the very front of her mouth, and even past the teeth. Again, she will likely grow out of it, though resources exist to help you if she doesn't.
Lisps that might be the sign of a developmental problem
The following two lisps are not a normal phase in speech development, and speech-language pathologists don't know what causes them. It is less likely for children to just grow out of them, and a child with one of these lisps should probably see a professional speech pathologist for help.
- Lateral lisps are S's pronounced out of the side of the mouth. They are usually described as "slushy." Think of Daffy Duck's wet, spitty pronunciations and you'll have the idea. This is the sort of lisp that I had as a child, and back then it was called by the much less politically-correct name "lazy tongue."
- Palatal lisps occur when a child presses her tongue against her palate -- the roof of her mouth -- further back than the S belongs. These lisps are uncommon and don't even sound much like S's to most listeners: they sound more like the Welsh /ll/ sound, a sort of top-of-the-mouth H.
"Curing" a lisp
It's important for a speech pathologist to establish whether a child has problems with language or problems with pronunciation. To that end, she might give the child a series of words and ask him if he can tell the difference (e.g., "saw" and "thaw"). If he can't, then what he has is not a lisp; he may have a developmental phonological disorder of some type, or he may be partially deaf. In either case, he will probably need professional help of a different sort than a speech pathologist can provide (though a speech pathologist might be able to work in tandem with the doctor who diagnoses the problem).
If the child does have a lisp, then he can go through a series of exercises to change his pronunciation. Any child with a functional speech disorder -- so long as that's all he has -- can learn proper pronunciation of sounds, given enough time. Much of this training is simply breaking out of one habit of speech and learning a new one.
Of course, plenty of people continue to lisp into adulthood, especially if they did not go through speech therapy as children. Some of them are not bothered by this; since lisping (unlike some other speech impediments) does not make a person hard to understand, he or she can usually function just fine in society, and some even develop a kind of pride in their unique way of speaking. It certainly didn't seem to cramp Moses' style.
Other people, however, feel awkward and ashamed of the way they speak, and worse, they're under the mistaken impression that it's too late to fix it. It's not. Speech therapy can work for anyone.
Speech impediments and culture
When I think of all the fictional characters who lisp, I ask myself why the actors who voiced them chose to represent them that way. I'm pretty sure I've never seen a lisp portrayed without mockery: think of Biggus Dickus in Monty Python's Life of Brian ("theveral theditiouth thcribeth from Thaetharea"). To my knowledge, lisps in movies and television programs are never treated neutrally -- as "just" the way a character talks -- but are always intended to be funny, cute, or pathetic. (Do let me know if you can think of an exception.)
Lispers are especially common in cartoons. Sylvester the Cat (whose name cruelly contains two esses!) and Daffy Duck are probably the most famous cartoon lispers; Daffy was actually modelled after one of the producers at Warner Bros., who, the story goes, enjoyed the voice of the character without recognizing himself in it.
Both Sylvester and Daffy were voiced by Mel Blanc, who seemed to like giving functional speech disorders to his characters. Tweety Bird has problems with a whole lot of sounds; his most famous catchphrase alone screws up an /s/, a /k/, and a /th/. Porky Pig stutters; Foghorn Leghorn does too, in a way. Elmer Fudd, who was originally designed by Arthur Q. Bryan and only later voiced by Blanc, famously has trouble pronouncing the /r/ sound; Google even has a page dedicated to "Fuddifying" searches.
Bugs Bunny is probably the worst of all: he has a very serious case of a Brooklyn accent.
I got much of my information for this node from this superb resource: http://members.tripod.com/Caroline_Bowen/lisping.htm
It includes contact information for speech pathologists in the U.S. and Canada who can help you or your children if you are concerned about lisping.
Thanks to rootbeer277 for extra Warner Bros. trivia.
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