Final answer:
Two challenges to Piaget's theory include a preference for a continuous model over discrete stages of cognitive development, and evidence that children achieve cognitive milestones earlier than he suggested. Researchers like Courage & Howe, Siegler, and Baillargeon have been instrumental in advancing these critiques.
Step-by-step explanation:
The question asks to discuss two recent challenges to Jean Piaget's theory of cognitive development. The first challenge is that contemporary studies suggest a more continuous model of cognitive development rather than Piaget's theory of discrete stages. Researchers like Courage & Howe and Siegler have provided insights into this critique. The second challenge comes from studies showing that children reach cognitive milestones earlier than Piaget proposed. Baillargeon and others have shown that infants as young as 3 months demonstrate an understanding of the properties of objects, which counters Piaget's claim that these cognitive skills develop slowly over time due to limited experiences.
Overall, these challenges lead to a view of cognitive development that leans more towards gradual and continuous improvement in cognitive abilities from a very young age, as opposed to Piaget's stage-based, stepwise pattern of shifts in cognitive abilities.