There are two possible interpretations of causal coupling here, and it is important to be clear about which one is implied by C&C.
A. Asymmetric influence: environmental features have a causal influence over inner processes. It may still be the case that we can change the external environment and that affects competence and behavior of the subject. If you take my diary away from me I won't be able to remember all my engagements. The diary prompts my recall of memories, but there is no need to go further and say that because the diary has a causal influence on me that it is thereby part of my memory, or the cognitive processes that allow me to remember. It would be a mistake to make this claim simply on the basis of a causal connection.
B. Symmetric influence: the inner and outer features have a mutually constraining causal influence on one another that unfolds over time. It is not simply that the diary prompts or causes, as input, various cognitive processes to unfold in my brain; rather, the external process of retrieving the information from the diary and the concurrent processes in my brain jointly govern my future behavior. This is what Menary calls cognitive integration (2006, 2007, this volume).
This distinction is important because, critics of EM, such as Adams and Aizawa (2001, this volume) are working with interpretation A, but Clark is working with B. Hence there is a misunderstanding between exponents of EM and their critics. The critics may wish to claim that although EM is supposed to endorse B, very often A is what is endorsed, and A is not a constitutive thesis. Exponents of EM must be careful to indicate when and why they are using interpretation B. (Menary, 2010, pp. 3-4)Ok. I don't see that reciprocal coupling matters at all. Take the original story about the bimetallic strip in a thermostat. You get reciprocal coupling there, but not extended strip expansion.
To begin, we may observe that the mere causal coupling of some process with a broader environment does not, in general, thereby, extend that process into the broader environment. Consider the expansion of a bimetallic strip in a thermostat. This process is causally linked to a heater or air conditioner that regulates the temperature of the room the thermostat is in. Expansion does not, thereby, become a process that extends to the whole of the system. It is still restricted to the bimetallic strip in the thermostat. (Adams and Aizawa, 2001, p. 56)Adams, F., & Aizawa, K. (2001). The bounds of cognition. Philosophical Psychology, 14(1), 43-64.
Menary, R. (2010). Introduction. The Extended Mind. Cambridge, MA: The MIT Press. (pp. 1-25)