Robbie Case is a significant figure in developmental psychology known for his work related to Piaget's theory of cognitive development. He proposed the 'robustness' of cognitive structures and argued that children's reasoning abilities develop through specific stages, similar to Piaget's stages, but with a greater focus on the processes that underlie these cognitive transformations. His work emphasized the importance of understanding how children actively construct knowledge, blending insights from Piagetian theory with contemporary research on cognitive processes.