Multiply controlled verbal operants: an analysis and extension to the picture exchange communication system.

Andy and colleagues unpacked each PECS phase using Skinner’s verbal operants. They asked, ‘Which operants are in play when a child hands a picture of a cookie to get the cookie?’

The paper is conceptual. No kids were tested. Instead the authors mapped training steps to ‘multiply controlled’ mands and tacts—responses that are strengthened by both wanting the item and seeing the item.

They produced a clear road map. Phase 1 teaches a pure mand. Phase 3 adds tact control. By Phase 6 the child is commenting under both motivative and discriminative control.

The map shows where to insert extra teaching if the child can request but not label, or label but not request.

Alfuraih et al. (2024) later showed the map works in real life. Three non-verbal children with severe ID learned to request, and the skills lasted—an empirical extension of the 2004 logic.

Gilroy et al. (2023) went further. They gave autistic children with ID either PECS cards or a tablet app. Both groups made equal gains, proving the operant analysis holds no matter the hardware.

Danitz et al. (2014) looked across dozens of studies and found PECS works best for preschoolers with ASD plus ID. That synthesis includes the very operant framework Andy laid out, turning theory into an age-and-ability matching rule.

Use the map to decide your next target. If the learner already hands the picture for the item but never names it, stay in Phase 3 and add tact probes. If the child labels the cookie when it’s in sight but won’t ask when it’s gone, program pure mand trials with the cookie hidden. The paper gives you the language to write precise, operant-based objectives and to spot why progress stalls.