When the researchers examined the children three years later, they found that children who had a larger oral vocabulary at age 2 were better prepared academically and behaviourally for kindergarten, with greater reading and maths achievement, better behavioural self-regulation, and fewer acting out or anxiety-related problem behaviours.
And if the child has a vocabulary at age two, they must have absorbed all these words before they were two.
“Externally he seems to be making no progress, but all of a sudden he says a word. Then for a long time he uses only two words, and seems discouragingly slow to go any further… Within a space of three months, the child who was almost dumb, learns to use easily all the varied forms of the noun, suffixes, prefixes and verbs. And, in every child, all this occurs at the end of the second year of his life.” — Dr. Maria Montessori, The Absorbent Mind