The concept of a response frame is useful when the response at issue includes contextual control over an overarching operant that includes specific assigned forms. Skinner's concept of an autoclitic frame, described in the previous chapter, is an example (e.g., "when you hear _____ you will receive a _____"). Imagine that a person hears a variety of sentences, such as "when you hear a knock you will receive a package" and "when you hear the recess bell you will receive a break." Eventually any term can be placed into this "autoclitic frame" and the listener may know what to expect. Just as a picture frame can hold many pictures, a response frame can include different formal features while still being a definable instance of an overall pattern. "Frame" is not a new technical term, and it is not a structure, mental entity, or brain process. It is a metaphor that refers to a characteristic feature of some purely functional response classes: the behavioral class provides an overall functional pattern, but the current context provides the specific formal features that occur in specified parts of that pattern.