Who was the first theorist to observe and document stages of physical development?

The correct answer is based on Arnold Gesell's pioneering work in child development, particularly in documenting the stages of physical development. Gesell was one of the first psychologists to systematically observe children and categorize their growth patterns, focusing on the relationship between physical maturation and behavioral changes. His approach involved careful, longitudinal studies of children, allowing him to outline distinct stages that reflect normal physical and motor development.

While Jean Piaget is well-known for his theories of cognitive development in children, he concentrated on how children think and learn rather than their physical growth. Sigmund Freud is recognized for his psychosexual stages of development, emphasizing emotional and psychological aspects rather than physical changes. Lev Vygotsky’s theory primarily addresses social interactions and cultural influences on learning and development, moving away from a strict focus on physical growth and instead emphasizing cognitive development through social contexts.

Gesell's focus on the development of motor skills and physical capabilities set a foundation for later research in developmental psychology, making him a key figure in the study of physical development stages.