Development is the qualitative progress of a child, usually divided into 4 categories:
1. Gross motor: It refers to the gross motor activities like sitting, standing etc. As mentioned earlier, it is the least important and least reliable criteria to judge the overall development of a child, though the parents lay the most emphasis on it.
2. Fine motor: It refers to development of fine motor skills by the child that requires a fine co-ordination of his small muscles. Most of the things that the child learns to do with his hands in a dextrous fashion come under this category e.g. eating, grasping objects etc.
3. Social: It includes those milestones in which the child learns to interact with the parents and other human beings. Examples are smiling, laughing, playing etc.
4. Language: It refers to the development of the child by which he understands the mother tongue/other languages (called receptive language development) and also expresses his feelings in them (called expressive language development).
In human beings, like in animals, are there “critical periods” of development i.e. certain skills have to be learnt within a particular time frame, after which the “window of opportunity” is permanently and irrevocably lost? The answer fortunately is no. However the concept of “sensitive period” is there, according to which some skills are best-learnt and mastered during particular periods in the life cycle, although late emergence of them is not impossible. The establishment of basic trust in infancy and the development of language are 2 areas of competencies that have been postulated to be difficult to achieve beyond their sensitive periods.