Final answer:
Jerome Kagan's research suggests that temperamental characteristics such as shyness and boldness show consistent stability from infancy through early childhood. Cognitive milestones such as object permanence and predictive abilities are also present early on, reflecting stable cognitive development.
Step-by-step explanation:
According to Jerome Kagan, temperamental categories like shyness and boldness show considerable stability from infancy through early childhood. Early developmental psychologists such as Jean Piaget highlighted significant changes in cognitive abilities from infancy to adulthood. However, Piaget's perspective differed from contemporary psychologists who have found that cognitive abilities, including the understanding of objects and their properties, develop at a younger age than Piaget suggested.
Young children, especially during the preschool age (3-5 years old), demonstrate a steady progress in their cognitive development. They not only learn names of colors and count but also make decisions, understand basic time concepts, and enjoy symbolic play. Cognitive milestones, such as the development of object permanence and the ability to predict outcomes, are achieved much earlier in life, indicating a stable progression in cognitive development.