The ABCs of /s/ and /z/

Watermarked sz Photo (2016-06-16-1308)

We all know that there are various reports, research, and information regarding the age of acquisition of speech sounds. How in the world do we decide which ones to use for determining if a student has an articulation disorder? Are you at the mercy of your school system and the age norms they have decided to use?

We have searched many resources and found The Iowa Articulation Norms Project and its Nebraska Replication to be a very helpful read.

When it comes to /s z/, this article raises some great points. Believe it or not, the projects found that acquisition curves for /s z/ did not reach 90% criterion until age 9! Considering that these sounds are so common in English, do we really want to wait that long?

The researchers identified that 80% of responses were adequate by age 7 with slow growth after that. We love the recommendations they provide to look at /s z/ at age 7 with some additional considerations.

To wait or not to wait, that is the question

If a 7-year-old uses an acceptable production of /s z/ in any context (including clusters), it may be best to delay intervention. We should also consider if the child is stimulable for any acceptable production or if they are still waiting on those two front teeth for Christmas! Check again for these same factors at age 8 and again at age 9…but by then we should intervene for sure if errors in production (and educational impact) are still evident.

Speaking of educational impact…

Us school-based SLPs ALWAYS have to consider educational impact. More often than not, with articulation, this is especially evident in the social context. There can definitely be justification to start earlier based on documentation of impact on educational performance!

Too late for lateralizations?

Lateralized productions are not likely to improve with age without intervention. Therefore these should not be considered developmental errors. Early intervention can be considered (as early as preschool) given that the child demonstrates a response to treatment and does not appear to be improving on their own.

Our favorite reference: Smit, A. B., Hand, L., Freilinger, J. J., Bernthal, J. E. & Bird, A. (1990). The Iowa articulation norms project and its Nebraska replication. Journal of Speech and Hearing Disorders, 779-798

Elissa’s personal perspective

You know you’re an SLP mom when you shudder at your two year old’s dentalized /s z/. And you try SOOOO hard not to help her fix it! Then at age 3 it hasn’t changed AT ALL…what’s a mom to do?!?!

So you provide models, show her in the mirror where her tongue goes…


She’s only 3!

By age 4 she is stimulable (mom breathes audible sigh of relief). Maybe she won’t need speech…

So now she’s 5 (5 ½ if you ask her) and ALL BY HERSELF she produces the most beautiful /s/ and /z/…well, most of the time. Sure she slips now and then but come on…she’s only 5!

It will all be ok!

What age norms do you utilize for /s z/?

Image courtesy of fantasista at

Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s