Assessing the acquisition and generalization of two mand forms with adults with severe developmental disabilities.
PECS beats manual sign for speed and generalization when teaching first mands to adults with severe ID.
01Research in Context
What this study did
Chambers et al. (2003) asked which mand method works faster for adults with severe ID: PECS or manual sign.
They used an alternating-treatments design. Each adult got both methods in mixed order.
The team tracked how fast each person learned to ask for items and whether the skill carried over to new places.
What they found
PECS won. Adults reached mastery sooner with pictures than with signs.
Skills taught with PECS also showed up more often in new rooms and with new staff.
How this fits with other research
Valentino et al. (2019) backs this up. Their quick pre-test also sent non-vocal learners to picture exchange first.
Van der Molen et al. (2010) seems to disagree. Manual sign plus prompt delay sparked new vocal words in non-vocal children with autism. The gap is age and diagnosis: kids with autism may gain speech through sign, while adults with ID gain speed through pictures.
Savaldi-Harussi et al. (2025) extends the PECS edge even further. Toddlers who were stuck on Phase 1 took off when video clips were added to the cards.
Why it matters
If you serve adults with severe ID, start with PECS. You will see faster mastery and better generalization than with sign. Keep sign in your toolbox for younger or autism cases where vocal growth is the goal, but let the data guide you. Run a quick probe, pick the winner, and move.
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02At a glance
03Original abstract
The purpose of this study was to determine whether manual sign or the Picture Exchange Communication System (P.E.C.S.) (Frost and Bondy, 1994) would be more effective in teaching mand skills to adults with mental retardation in the severe and profound range. Four participants were taught to mand for four reinforcing items using both communication modalities, in an alternating treatments design. Three of four participants demonstrated criterion performance across all four mands using P.E.C.S. first. Two of those three participants later demonstrated criterion performance for the mands using manual sign. The fourth participant was removed from the study during training due to illness, but her progress indicated greater acquisition with P.E.C.S. Generalization probes conducted at participants' respective residences showed that three participants demonstrated generalization across settings using P.E.C.S., and two participants demonstrated generalization across settings using manual sign. Participants were also more likely to mand for reinforcing items not present using P.E.C.S. than using manual sign.
Research in developmental disabilities, 2003 · doi:10.1016/s0891-4222(03)00042-8