Beyond the Brain: Difficult Metaphors

Continuing coverage of Beyond the Brain, by Loise Barrett. The first part of the extended blog review is here, there is a succinct published review in PsychCritiques.
 
Chris asked me a question over at Manchester Psychiatry and I realized three important things: 1) I have written a lot about Beyond the Brain, 7 posts. 2) I still have a few more posts to write. 3) I better do that soon. 


This post is the most "asking for help" of the things I have left to write. It is about metaphor. I love a good metaphor, and most of the metaphors in Barrett's book were good. However, there are two pairs of metaphors that just aren't working for me, and they are somewhat common metaphors in the complexity/dynamics systems literature. In particular, I found the ‘short leash’ vs. ‘long leash’ analogy weird, similarly the ‘loose coupling’ and ‘soft assembly’ analogies have never quite gelled for me. I would appreciate some help figuring out why these labels make sense.

 Leash Length

‘Short leash’ refers to situations in which a central control mechanism has a high degree of control over all the structure in a set of behaviors, as when an owner (the central control mechanism) has tight control over a dog on a short leash (the dog being the body doing the behavior). ‘Long leash’ refers to situations in which the central control mechanism does little work, because the structure of the organism-environment interaction takes care of a lot of things you might otherwise think requires control, as when an owner of a very well controlled dog still gets the desired behavior even with a very long leash. Barrett invokes this metaphor to help readers understand how a properly built body can engage in sophisticated movements without each little detail being controlled by the brain. Good constrained-dynamic-systems stuff, which I agree with.
But while I like the message, the metaphor doesn’t quite work, for me. I find it confusing, I think, because there are two candidate ‘central controllers’ in the dog walking situation, the human’s brain (or the human more generally) and the dog’s brain. Thus I'm not sure what to think when Barrett uses mars-exploring robots as an example of the short leash vs. long leash distinction. Of particular interest is a new breed of distributed-control robots which are being developed, which spread out and explore without continuous human input... you know, cause any signal given by a person on Earth takes several minutes to reach Mars, so you standard video game style controls don't do much good. Instead of building one big robot that can handle anything (you hope), the new approach is to have lots of robots that will each "know" a little something about their local surroundings, and so can overcome challenges as a group, such as finding good paths around obstacles or implementing an idealized random-search pattern for resources.
However, because I don't know whether the human brain or the dog brain is the central control mechanism, I'm not sure what to think about the robots. The well healed dog's behavior is based, almost completely, upon a modified dogs brain. The mars robots could just as easily be controlled by a relatively centralized control system, which would render the 'long leash' metaphor odd. If, on the other hand, there was no centralized control mechanism on mars, and the robots acted in a very autonomous-but-coordinated fashion, accomplishing goals that no central mechanism is regulating, then I'm not sure that there is any leash. Thus an example of a robot that can explore mars correctly without direct human control doesn’t necessarily mean that there isn’t a strong central-control element, it only means there is not a ‘short leash’ connecting it to earth. This metaphor isn't too bad, it just gets muddled, and there should be a better metaphor we could use.

Coupling Strength

‘Loose coupling’ and ‘soft assembly’ cannot be criticized in the same way, because those terms suffer primarily from not drawing a metaphor to a clear and concrete situation. At the least, I can't really tell what situation they are trying to invoke. The gist of these terms can be easily gathered in context, but the book would have been stronger if better metaphors could have been created. So far as I can tell, the idea is to contrast something assembled like a die - with the relationships between the numbers on the side rigidly determined - versus something like a Rubic's Cube - where many patterns can be quickly made by rearranging the parts. Of course, that example is not very good. The skin of an octopus might be a good example of a soft assembly system, it can become spiky or smooth, change color, and variously serve countless functions by becoming a series of different tools, while still being one thing. 
Why loose or soft vs. hard? I can't say. I intuitively know what it means for two things to be tightly coupled, but when I use that to think about two things being loosely coupled, I just end up with the conclusion that they are connected, but will fall apart easily. Is the joint between two train cars a tight or a loose coupling? Well, it usually seems tight, but a big enough jostle and they fall apart, and the swivel of a lever and they come apart. If the lever is half-way, then the first car still pulls the second car, but things at the connection point are loose. Similarly, when I think of a softly assembled structure, I think of the block towers my children build and knock down... because they are not assembled more strongly. Or maybe I think of a structure made out of toothpicks, with marshmallows as the joints. I don't think either of these ideas are anywhere near what the author is trying to invoke, but it is where the metaphor seems most naturally to lead. 
I know these terms comes from computer science and dynamic systems work, and I know that sometimes you have to use what others give you, but the labels are so unintuitive that something better must be possible. Any help?