A baby grasps for his or her rattle at 3 months of age but cannot quite get hold of it. However, by 11 months, the baby is holding and moving the rattle with total control. This is an example of the .

Principle of hierarchical integration.

Explanation:

Principle of hierarchical integration is the level of growth in which simple skills tend to grow independently .In time, these skills get united as complex skill in the child as development take place.

According to the question, baby is not able to have proper grip over rattle even after grasping.This separate skill develops accordingly with the growth of baby .He/she is able to grab the rattle through gripping as well as move it for rattling as complex skill is developed.