Equivalence class establishment, expansion, and modification in preschool children.

The team worked with preschoolers who had no diagnosis.

Kids learned four two-choice matching games with made-up shapes.

Same shapes stayed on the screen as the correct choice each time.

Later the researchers added new shapes and flipped some rules.

They watched to see if the children’s groups of "same" pictures held together.

Children built the classes quickly when the layout never changed.

They also added new pictures to the group without extra teaching.

Most kids even flipped the whole class when the correct choice swapped sides.

In short, preschool minds can build, grow, and turn around equivalence sets.

Lerman et al. (1995) saw the same flip task four years earlier.

Only two of five kids in that study managed any re-sorting.

The difference: C’s team changed which picture was correct on every trial.

R’s team kept the same picture in the same spot, making the flip easier.

So young children can reverse classes, but only if the task stays simple.

Arntzen et al. (2018) later showed adults need a short delay warm-up to reorganize.

The preschool brain can do it without help, provided the screen layout is stable.

Keep your match-to-sample layout consistent during early lessons.

If you must swap the correct picture, do it slowly and probe for class breaks.

Watch for accidental reversals when you add new items.

A steady screen gives you faster equivalence gains and fewer tears.