“…However, we contend that it is important, in the interest of fairness, to acknowledge the extensions and amendments to Skinner's account of verbal behavior that have emerged in the decades since the book was published. Several authors have, for instance, considered extensions and alternatives to Skinner's definition of verbal behavior that take into account the extensive research literature on derived relational responding (e.g., Barnes-Holmes, Barnes-Holmes, & Cullinan, 2000;Chase & Danforth, 1991;Hayes, 1994;Hayes, Barnes-Holmes, & Roche, 2001;Hayes & Hayes, 1989Leigland, 1997Leigland, , 2007. In addition to these important conceptual advances, behavior analysts have also undertaken productive basic and applied research programs that have contributed empirical support for a synthesis of Skinner's taxonomy with contemporary approaches to verbal behavior (e.g., Barnes-Holmes et al, 2000;Barnes-Holmes & Murphy, 2007;Murphy, Barnes-Holmes, & Barnes-Holmes, 2005;Rehfeldt & Root, 2005;Rosales & Rehfeldt, 2007).…”