Define "cognitive development" and name one key theorist associated with it.

Cognitive development refers to the progression of skills and processes related to thinking, reasoning, problem-solving, and understanding the world. It encompasses how individuals acquire, process, and store information throughout their lifespan. One of the key theorists associated with this concept is Jean Piaget, who proposed stages of cognitive development that describe how children's intellectual abilities evolve from infancy through adolescence. Piaget identified four primary stages: sensorimotor, preoperational, concrete operational, and formal operational, each characterized by distinct ways of thinking and understanding.

In contrast to other options, the focus of cognitive development is not solely on physical growth or emotional intelligence. While emotional intelligence is an important aspect of overall development, it is different from cognitive processes. Furthermore, while Lev Vygotsky's work emphasizes social interactions and cultural influences on learning, it is more about the social context and less about the specific cognitive stages as defined by Piaget. Therefore, the association of cognitive development with Jean Piaget accurately encapsulates the essence of this area of study.