While no two children are alike in development, the process does follow several general patterns. Development proceeds from generalized activity of the whole body to specific individual responses. Large-muscle control proceeds from head to toe. First infants learn to control their head, then they crawl on their belly, dragging their legs by pulling with their arms, and finally they control their legs and feet in walking. Fine-muscle control begins with flexion and proceeds to extension.
Movements proceed from symmetry to asymmetry.
Some infants and toddlers undergo developmental testing for a specific reason, such as an obvious delay in sitting, walking, or speech. The results of such tests should be interpreted cautiously. While it is important not to delay too long before investigating developmental lags, it is wise to be very certain about a test result before making dire predictions.