There is an orderly sequence to the development of a young person's behaviour in every area of functioning.
This development doesn't cease when an individual reaches adulthood. In all human beings, sequential patterns of development and --- continue into old age. An obvious example of a developmental sequence is that associated with motor development during infancy. By the time babies are about two month old, they can raise the head and chest while lying on the stomach - a feat. that enables them to scan a world beyond the crib. Between the fourth and seventh months, hand - eye coordination has improve enough to enable them to reach out and grasp almost any object within range: mother's glasses, father's nose, the mobile dangling overhead. By seven months, they usually can sit up without support, and a few months later, they are able to hoist themselves into a standing position while holding on to furniture. At ten months, most babies are accomplished crawlers capable of wreaking havoc on all law - lying areas of the house. And finally, around the first birthday, most infants take their first step - an event that opens a whole new realm of experience. Such orderly sequences appear in the development of cognition, language, social and emotional development as well and can be described in terms of norms, averages derived from observing many individuals. The age at which a particular baby masters any skill may vary widely from the norm. Variations in the rate of development depend on the hereditary & environmental influences that combine to affect all aspects of development.