For example, when an infonl is making sounds while in the presence of a par-ent and says "ma-ma," the parent may rush to tho infant, show signs of delight, and say, "Oh, you said 'ma-ma'!" This positive response from the parent increases the chances that the infant will repeal those sounds. Likewise, speech that elicils no response or is ignored is less likely to be repeated.
We usually express our thoughts to others and we know that people understand us if they react a certain way. It's a neat idea that we learn language through how people react to what we say.