Need for action
And theory
If your child is past the age at which most children normally start putting two words together – in the second half of the second year, if your child still has only single words, or if his or her only word is for cat, dog, bird, horse, bus, car, lorry, or to ask for his or her favorite drink, or to say hello or goodbye, it is not obvious what the importance or relevance is of any of the theories here. You might reasonably say to yourself: I don’t care which theory says what about the situation as long as my child just starts putting words together.
But theory can make the action more effective and work faster.