Brenda Allen, M.A., CCC-SLP created this resource to share with families about the complexity approach. She and other San Diego Unified SLPs have utilized this document to explain the principles of the complexity approach to families for children who speak English. Jessica A. Barlow, PhD. and Laura Garcia-Maxey created a similar document to share with families whose children speak Spanish.

The hierarchical structure demonstrates that children who are taught complex sounds often learn treated and untreated sounds due to the relationships amongst sounds. For example, if a child is missing many sounds and is taught a three-element cluster (e.g., /str‐/), it is predicted that he or she will also learn some missing two-element clusters, affricates, fricatives and stops. Conversely, if a child is missing many sounds and is taught a stop (e.g., /k/ or /g/), it is predicted that /k/ or /g/ will likely change, but not other sounds. Teaching complex sounds leads to rapid change and gains in intelligibility. Please see the Implicational Language Laws document for specific citations regarding each identified language universal.