Montessori introduced several concepts to explain this work, including the absorbent mind, sensitive periods, and normalization.[
The first plane extends from birth to around six years of age. During this period, Montessori observed that the child undergoes striking physical and psychological development. The first-plane child is seen as a concrete, sensorial explorer and learner engaged in the developmental work of psychological self-construction and building functional independence. Montessori introduced several concepts to explain this work, including the absorbent mind, sensitive periods, and normalization.[36]