What is the PRIMARY distinction between Phase 3 and Phase 4 of PECS?

The primary distinction between Phase 3 and Phase 4 of the Picture Exchange Communication System (PECS) lies in the shift from requesting single items to requesting *sentences* and demonstrating an understanding that pictures represent *spoken words*. PECS is a structured intervention designed to teach individuals with autism or other communication challenges to initiate communication by exchanging pictures for desired items. Phase 1 focuses on establishing the foundation: teaching the individual to exchange a single picture for a desired tangible item. For example, a child might exchange a picture of a cookie for an actual cookie. Phase 2 builds on this by expanding the repertoire....