Millikan, in 'Biosemantics', points out that human minds separate the 'indicative' and 'imperative' functions of their representational system. (Beliefs represent how the world is; desires, how we want it to be. Either by itself is impotent: beliefs are motivationally inert; desires, blind.) Many animals have no such separation. When ants detect the oleic acid of a decaying corpse, they inevitably carry it out of their nest. There is a strict connection between stimulus and response. We cannot separate the indicative representation (of the corpse) from the imperative (to get rid of it). These are not two distinct states within the ant's cognitive system.
Without decoupled representation, there is no separation between identification and action, stimulus and response. This in turn leaves no room for practical reasoning, i.e. cognition which relates means to desired ends, by way of conditional beliefs ("If I perform behaviour B, then I can achieve goal G"). The importance of this will become apparent in my next post.
Sterelny writes (Thought in a Hostile World, p.31):
True beliefs are a "fuel for success": they form an information store about the world that advantages the animal in many different actions, but they are not tied to specific behaviors.
Decoupled representation aids behavioural plasticity, but how does it tie in with the two types of flexibility previously mentioned (i.e. robust tracking and response breadth)?
I think decoupled representation is conceptually, but not practically, independent of robust tracking. Sterelny grants that single-cued tracking could in principle produce decoupled representations. However, he considers it unlikely in practice for such a combination to evolve, as single-cued tracking is relatively unreliable, which decoupled beliefs cannot afford to be.
The relation with response breadth is more interesting. Sterelny argues that "decoupled representation evolves as response breadth increases. It is nothing but very broad-banded response." (p.34) It isn't clear to me that they are the same thing. An animal might choose between a broad range of options on the basis of immediate, functionally-specific stimuli (thus demonstrating response breadth without decoupled representation). Conversely, an animal might utilize long-term memory and decoupled representation to make a binary decision (i.e. a relatively narrow response breadth). So again, I think we should hold decoupled representation to be conceptually distinct from response depth, even though they may be linked in more practical ways. Though I'm not certain I've understood him correctly, I think Sterelny's main point here is that decoupled representations will help an animal to make successful choices, when faced with a broad range of possible responses. So they'll tend to go together -- but this is an empirical rather than conceptual truth.