Adams & Maher write,
It is important to see that Haugeland’s and C&C’s arguments share a structure. They argue that the mind extends because there are external items (a road, a notebook) that are functionally equivalent to admitted parts of the mind (a map, a memory). And these external items are functionally equivalent to partsof the mind because the external items have the same high-bandwidth interactions that those parts of the mind have to other parts of the mind.Now, I think that Haugeland's argument is actually much more ambiguous. To my mind, there is a bit of operationalism in the San Jose case, wherein he implicitly assumes that any way of getting to San Jose is the performance of a cognitive task. Then, there is the high-bandwidth (coupling argument) thing that does not require an inner-outer functional equivalence. Then there is this talk of functional equivalence.
Now, however one takes Haugeland's argument, I think it will not ultimately work out. In The Bounds of Cognition, we addressed each of the three ways of interpreting this argument.
And, I think that C&C also have an ambiguity about whether they want a functional equivalence argument or a coupling argument regarding Inga-Otto. When there is a discussion of both Inga and Otto, there are often allusions to functional equivalence (which is why the story involves Inga and Otto). But, the trust and glue coupling arguments do not really need to involve Inga.