Development of syntax in a retarded girl using procedures of imitation, reinforcement, and modelling.

The team worked with one girl who had an intellectual disability. She could not yet make full sentences.

They ran short discrete-trial lessons. The adult modeled a sentence, the child copied it, and a bite of candy followed a correct response.

Each week the criterion rose: first only singular sentences had to be right, later plural ones, then mixes. The design is called changing-criterion.

The girl quickly met every new criterion. Singular and plural declarative sentences both improved.

When new pictures appeared she still used the right form, showing the skill had generalized.

Bushell et al. (1968) taught just the plural morpheme five years earlier. The new study adds whole sentences, building on that early work.

Dudley et al. (2019) looked at many children with ID and saw flat syntax growth. Their group study seems to clash with this bright result. The gap is method: natural play versus tight one-to-one DTT with models and candy.

DeVellis et al. (1979) showed expressive training boosts receptive skills. The 1973 paper fits right in—start by having the child speak the form, not just hear it.

You can grow real grammar in kids with ID if you break it into small modeled steps and reinforce each success. Use a clear picture set, raise the criterion bit by bit, and probe with brand-new pictures to check generalization. The recipe is still fresh fifty years later.