“…Fourth, a number of researchers have used equivalence phenomena to develop a behavior analytic interpretation of symbolic meaning and the generative nature of grammar (Barnes & Holmes, 1991; Hayes, Hayes & Hayes, 1989;Wulfert & Hayes, 1988). Finally, recent findings have shown that equivalence is important to a behavioral analysis of many disparate areas of research, such as social categorization (Grey & Barnes, 1996;Kohlenberg, Hayes, & Hayes, 1991;), human sexual behavior (Roche, Barnes, & Smeets, 1997;Roche, BarnesHolmes, Smeets, Barnes-Holmes, & McGeady, 2000), as well as the advanced reasoning abilities of humans (Hayes, Gifford, & Townsend, 2001;Lipkens, 1992).…”