When gliding occurs, a child substitutes the liquid consonants /r/ and /l/ with glides like /w/ or /j/, as in saying “wabbit” for “rabbit.” It is a normal part of development in English-speaking children and typically resolves by age 5 or 6. Persistent gliding may reduce speech intelligibility and is treated as a speech sound disorder. SLPs use auditory discrimination, minimal pairs, and structured practice to help eliminate this process.
Barbara Dodd et al., “Phonological Development: A Normative Study,” Clinical Linguistics & Phonetics 17, no. 8 (2003).
Marilyn A. Nippold, Later Language Development, 4th ed. (Austin, TX: Pro-Ed, 2016).