Researchers focusing on verbal behavior development have identified several components that appear foundational to becoming verbal. These include conditioned reinforcement for observing adult faces, listening to adult voices, and observing two- and three-dimensional stimuli in the environment .
Observing people and objects in the environment provides a context for individuals to participate in verbal exchanges with one another.
These observing responses are operants, selected out by their reinforcers; thus, the stimuli that are observed must be conditioned reinforcers .
Therefore, it is the establishment of the reinforcer for observing that is the critical foundation for verbal development.