The answer to the blank space is habit. The concept explained in the question refers to Piaget’s Cognitive Development Theory, where infants until the age of two years would develop various cognitive growth through interacting with the environment.
There are six sub stages in this development stage – from reflexes (0-1 month), primary circular reactions (1-4 months), secondary circular reactions (4-8 months), coordination of reactions (8-12 months), tertiary circular reactions (12-18 months), and early representational thought (18-24 months).