Q: I have a client, 2.5 years, who substitutes “F” for “K,” “B,” “D,” “G,” and “T” in initial “R” and “L” clusters. “W” replaces the glides.  I am not concerned about the glides.  Is the child just over-learning the “F” sound?

The replacement of a single phoneme for a cluster is called “Coalescence.” Hodson and Paden define this as the “replacement of two adjacent phonemes by a single new one which retains features from both of the original phones” (Hodson and Paden, 1983, p. 16).

In your case, the child first substitutes w/r and w/l, and then she substitutes /f/ for each cluster that results –– f/dw, f/tw, f/kw, f/gw, f/kw, and so forth. She uses /f/ because it is labial, as is /w/.  She may perceive /l/ and /r/ as fricatives at her young age, therefore she selects a fricative as her substitute.

I would not be worried about any of this because of her young age. But if I were to address it, I would do the following: Accept the substitutions of w/r and w/l and teach the W-clusters with epenthesis. This means to add a schwa. For example, teach her to say the following:

Phonologists usually consider epenthesis a deviant phonological pattern.  However, I view it as a step toward the cluster.  If you watch little kids develop words with clusters, they often go through in a sequence of expanding skill.  Take the word “please” for example.  Many children begin by saying “pease.” Then they say “puh-wease” or “puh-lease.” Then they say “pwease” or “please.”

By adding the schwa, you are teaching the client how to hear the two separate consonants of the clusters.  You also are teaching her to produce the two consonants in a sequence that is easier.  You are changing the CCV into a CV-CV.

Reference

• Hodson, B. W., & Paden, E. P. (1983) Targeting Intelligible Speech. San Diego: College-Hill.