The discussion begins with an introduction from each of the speakers about the core of their work. Dr. Deacon emphasizes how his work had evolved over the years with a greater focus on why language has commonalities, expanding that discussion beyond mere issues of nature and nurture into the requirements of language itself. He argues that “We can only communicate symbolically with certain kinds of combinatorial constraints that come from the problem of maintaining reference” and it is that which leads to universal features of grammar and syntax.

The RFT team (largely voiced by Dr. Dermot Barnes-Holmes) then delves into stimulus equivalence and how it opened up the phenomenon of symbolic relations for behavior analysts. Across decades of research, it has become clear that non-human animals are unable to convincingly demonstrate their features while it is quite easy for neurotypical humans. Dr. Barnes-Holmes describes an evolutionarily plausible reason that might be.

He also notes that part of the difference between the positions is that RFT is built out of an attempt to build a theory in human language and cognition which has direct and immediate applied implications.

That leads to an extended discussion of what each approach expects of itself in terms of data – consistency with neurobiological data; ability to apply the analysis; and what each side can learn from each other. The discussion notes areas of contact but also areas of disconnection based both on analytic purposes and the conceptual and empirical traditions represented.