The phases of PECS:
How to communicate: spontaneous requesting - 2 person prompt- pick up, reach, release.
Phase 2 Distance and persistence: travel to communication partner, take symbols/PECS, persistence across obstacles.
Phase 3A - simple discrimination: highly preferred vs non preferred, 4 step error correction.
Phase 3B - Conditional discrimination - correspondence checks, 4 step error correction, find picture in books
Phase 4 - Sentence structure e.g. I want, using descriptive vocabulary e.g. colours. Quantity, size. shape.
Phase 5 - answering questions
Phase 6 - commenting