PHYSICAL DEVELOPMENT development and therefore must be seen in the context of the social, emotional and intellectual changes that occur through childhood. Child development theories reflect the philosophies of their various authors, but as the subject is so complex, they have often been formulated from a particular stance. For this discussion, two theories have been selected to support the genetic and environmental effects on physical change. Inherited influences can be both subtle and obvious, as can the more long-term effects of environment. The effects of both interact over many years from conception to old age; they are instrumental in changing the child as it physically grows and matures.