B. F. Skinner proposed a theory of Operant Conditioning to account for Language Acquisition
The bell in Pavlov's experiment became associated with food and the dog salivated at just the sound of the bell alone. In this case, the bell was a sign--a call to action.
The learning process for symbols, however, would be the same. Mother says, "Daddy," to the child each time Dad comes in the room. The child learns to associate the sound "Daddy" with the person.
3 Operant Conditioning: In some instances the behavior of children is shaped by the consequences of their actions. A complex theory of language Development based on this premise was developed by B. F. Skinner.
The baby, in the process of making vocal sounds, hits by chance upon the combination "da-da." Dad, upon hearing this immediately picks him up, swings him around and makes a fuss.