When a response is controlled only by a main thematic source, that response is usually not very interesting, especially when compared to a response that is multiply controlled. Key words in puns, poetry, or humor are interesting and amusing because of the effects of multiple control. If the listener is not affected by all of the multiple sources, they may not find the response especially interesting, or they may not “get it.” What typically makes a particular response especially appropriate is the strength it derives from some additional source other than the main thematic source. We call these additional sources secondary sources of strength.