I don’t mean this to be offensive in any way, I am genuinely curious.
Lisping occurs when you place the tip of your tongue against (or in between) your teeth. I cannot make myself lisp unless I do this. Placement of the tip of my tongue anywhere else will not create a lisp.
On the surface it seems like an easy fix: Don’t do that.
Are those who lisp unable to avoid such placement when speaking? Is their inability to speak without a lisp a matter of tongue control only?
mmm
I don’t know the answer to your question, but I can lisp by just moving my tongue just a tiny amount, from just below the roof of my mouth behind my teeth to just below the bottom of the teeth. Actually just by lowering the tongue just a bit while raising the tip. I don’t even have to move the tongue. I also get a lisp by moving the tongue between the teeth as described in the OP.
I think I have a slight lisp, though others say I don’t. I had a pronounced one as a kid, though, and had speech therapy for it. The object was to get me to place my tongue correctly* behind my lower teeth for the “s” sound, instead of behind my upper teeth on the alveolar ridge, which is what caused the lisp.
I never learned how to put the tongue in the proper place and have it feel automatic – nothing is an easy fix, once you’ve internalized something so basic over the years! – but I must have hacked some custom tongue placement, still on the roof of the mouth somewhere, that greatly lessened the problem.
Try moving your tongue around, and changing the shape and pressure. There’s quite a lot of variation between a perfect “s” and Sylvester the Cat. You can make something approximating an “s” sound, with a greater or lesser degree of lisp, with your tongue in a variety of positions all over both hard palates and upper and lower teeth.
*according to that therapist, anyway
It can usually be taken care of at an early age. For some people it’s as simple as becoming aware of the lisp and practicing the proper configuration of the mouth to pronounce the ‘s’ correctly. There can be more serious problems with the configuration of the mouth that make it difficult, underbites and overbites, but other problems with the tongue as well although I have no details on that. I have known a couple people from early age onward who had minor inconsequential lisps get worse as they aged, but also were easily corrected.
I have seen over my life that schools attempt to deal with this early on, teachers may be more aware of a speech problem than family members who are used to a child’s speech. Many school districts will provide some basic speech therapy for young children. There are likely a number of children who could have a problem following the loss of their ‘baby’ teeth. It’s pretty natural to lisp when your incisors fall out.
I assume some people have more serious physical or neurological problems leading to lisping. Something as simple as missing teeth could cause a problem also. The simple solution is tooth replacement, but if that’s not possible for some reason I can understand the difficulty an adult, especially an older adult would have learning to speak without a lisp as a result of tooth loss or other injury to the mouth.
A lisp is also a legitimate pronunciation mechanism in some dialects. Just ask someone from Zaragoza.
I encountered a fellow once with some kind of Hispanic accent who seemed to be lisping. I asked him if that was Castillian Spanish, he laughed and said “No, I just have a lithp.”.
I feel like I’m moving in the other direction…I feel like I’m developing a slight lisp. It usually gets worse the more formal I’m trying to speak. It’s kind of news to me, as I was featured on the news in a segment that gets re-shown and I just absolutely do not like the way I sound…
Whenever I get new front crowns, I lisp for about a week, and occasionally thereafter until mouth placement for the new shape becomes automatic. My current crowns are a little too long and if I speak rapidly, I’ll lisp.
That’s not a lisp, any more than saying “this thing” in a standard accent reveals a lisp.
I had a mild lisp as a kid, and went to a speech therapist. I don’t really remember the details except that it involved tongue depressors and squirt bottles. No, my parents didn’t squirt me in the face every time I said something with a lisp.
Really, I think my tongue was too large for my mouth, which made it easy for it to just poke my teeth. I guess the therapist worked since I don’t have a lisp now.
It’s a common misconception to regard the Castilian pronunciation as a lisp, but it isn’t. The “th” sound only appears on “z” and soft “c,” but not on “s”, which is pronounced as in English. Someone with a lisp would pronounce all those letters as “th.” In Latin American Spanish, all three letters are pronounced as “s,” and the “th” phoneme doesn’t exist.
When I try it, the movement of my tongue from a valid /s/ sound to a more /θ/ (unvoiced “th”) sound is very slight. My tongue is very, very nearly between my teeth for an /s/. I only have to move it slightly forward, or slightly change the groove of my tongue to move it forward.
From what I’ve read, a lisp is due to a lack of sibilance on the /s/ sound. And sibiliance is created by creating a small enough groove that you get this higher pitched hissing sound, rather than the lower pitched airy sound. So it would seem to me that the difference is always due to some small movement of the tongue.
So the issue is just that the /s/ sound is actually a sort of goldilocks sound, where you have to do it just right. Any deviation can lose the hissing sound, and thus sound like a lisp. I can even lisp by pulling my tongue further back into my mouth.
Edit: And I can get more of an /s/ sound by just changing the shape of my tongue, even when my tongue is definitely between my teeth. I just use further back on my tongue to actually produce the sound.
I seem to recall getting a lisp temporarily when I broke a front tooth. It was quite some years ago and I don’t exactly remember the details, but it definitely affected my speech. It’s amazing how much difference such apparently small things can make. It was one of those dental things that I was very, very happy to get fixed pronto! Not that there’s anything particularly awful about a natural lisp, but it’s bothersome when you acquire it suddenly.
One of my kids had a lisp. When they went to kindergarten on the very first day they got sent to a speech teacher. Using a mirror and showing proper tongue placement when speaking she got them to stop lisping in about an hour and they never did it again.
As a kid I had a very mild frontal/interdental lisp wherein my “s” and “th” were a bit mixed. It was subtle enough that it went unnoticed throughout my early childhood and I slipped through all the way until 5th grade before a speech therapist testing my class spotted it. I don’t know if it was because it was relatively subtle, my more advanced age or I just wasn’t that bright 
- but it took me considerably more than one hour to correct it.
I had after school one hour sessions I think once a week with a speech therapist for several weeks at least (I really can’t remember how long this went on anymore). Mostly endless practice and repetition reading passages from books back to her until it became natural rather than consciously controlled.
I do not know why, but fairly often, when I say “yes” it comes out as “yeth.” Not always, and no other instances. Weird. I think it may be more psychological than physiological.
Which I’ve always thought a cruel joke, name the condition a word they can’t say.
I have what people call a Gene Simmons tongue – it’s quite long, but ordinary in terms of whatever other dimensions a tongue would have (width, height). And I can pronounce my s’s perfectly.
But there was one day where I had a lisp. On that day, I was in a rollover car accident and bit my tongue as the car was tumbling. There was no long-term damage to my tongue, but it was good and swollen when I was talking on the phone with my insurance agent right after it happened. My tongue was “big” in a different sort of way that day, and what’s more, it was big in a way that my body couldn’t control, if that makes sense. The tongue is a muscle, and even a big muscle can be pretty well controlled if your body is working properly. But with all the blood flowing to my tongue, I couldn’t exactly control my blood vessels and the way they were moving.
In answer to the original point:
On the surface it seems like an easy fix
The issue is the speed at which we have to think and speak - about 5.6 syllables per second is the average, and that’s every second! There is literally no time to think about tongue placement.
There are tests where people are shon how to say the letter S (as in sssssnake) in a different way, and peple can easily do that, but when they try to say ‘sausages’, they can’t do it. A single three-syllable word is too fast to control, unless you say it very slowly.
A former colleague of mine has the kind of lisp in which she actually pokes the tip of her tongue all the way through her teeth, like a Ralph Bakshi character. I always wondered whether speech therapy couldn’t at least ameliorate the severity of that lisp.