Matching Pairs Concrete Operational StageOnline version This crossword puzzle is over key terminology related to Piaget's concrete operational stage. by Jennifer Paris 1 identity 2 conservation 3 decentration 4 seriation 5 reversibility 6 classification arranging items along a quantitative dimension in a methodical way understanding that objects have qualities that do not change even if the object is altered in some way. understanding that things that have been changed can be returned to their original state considering changes in more than one dimension understanding that changes in one quality can be compensated for by changes in another quality organizing objects by a variety of characteristics (size, color, shape, etc.)