The first step in an analysis of verbal behavior is to classify the different types of relationships between controlling variables and verbal responses. This classification is based upon 3 factors: the musculature involved in the behavior (either those muscles used in speaking or writing), the type of controlling variable (verbal stimulus, non-verbal stimulus, or establishing operation), and the nature of the controlling relationship (point-to-point correspondence, formal similarity, or neither). This classification represents the basic building blocks of verbal behavior. As you’ll see in later lessons, they often combine with one another or can themselves become controlling variables for other types of more complex verbal relationships. Let’s look at echoic behavior first.