Developmental norms refer to milestones and stages of physical, cognitive or emotional development expected at any given age. Physical developments refer to changes in the body and the ability to control it. Cognitive developments refer to changes in the mind and psychology and to growth of knowledge. Emotional developments are changes to the ability to handle emotions.
While all humans are different and grow, change and mature in different ways, certain developments are expected around particular ages. Patterns of development and learning are similar across all the diverse populations in the world, lending credence to the theory that human development is standard across the species. Psychologists and doctors study development to understand different ways to help humans grow to the best of their ability. Many parents have an active interest in their child's development and whether or not they are demonstrating normal behaviors at certain times. For example, one physical developmental norm a parent might be concerned about is the age at which a child starts walking. While it is normal for a child to begin walking at any time in their first two years, it is an important milestone to monitor to ensure the child does not have a developmental disorder.