Your child may have an 'atypical' lisp when their 's' sound is not clear and crisp, yet your child is not seen to poke their tongue between their top and bottom teeth. This is most likely due to the air flowing out the sides of the mouth, instead of the front of the mouth.
Place your open hand two centimetres from the front of your mouth, horizontally and make a long 's' sound. You should feel the air/breath flowing out of your mouth from the very centre. Children with a typical developmental lisp should mimic this airflow even though part of their tongue is out of their mouth too.
If the air is not flowing out the centre of a child's mouth and can be felt/heard flowing out from both sides of the mouth instead, this is most likely a 'lateral lisp' and it is recommended that you contact a speech pathologist. This means that a child has learned an incorrect habit of where to place their lips, cheeks and tongue when saying the 's' sound and intensive exercises are recommended.
If your child is still producing a 'typically lisped' 's' sound at age four years, six months with their tongue showing between their teeth, you can help them at home before choosing to consult with a speech pathologist. In the next blog post, I'll explain some techniques to help your child with their lisp at home using the Flexible Speech App.
Please feel free to contact me if you have any questions.