Is human consciousness strongly emergent? This question first requires defining "strongly emergent," which I will define as: a phenomenon that is supervenient on a substructure but that is fundamentally irreducible to laws governing that substructure and which is capable of exerting downward causation on that substructure. That's a mouthful, and for those who haven't read the second post in this series, "Weak vs. Strong Emergence," it may be worth the five minutes to do so. That said, it appears that human consciousness meets there criteria: despite decades of intense investigation, science has so far been unable to demonstrate how consciousness is reducible to the biological structure of the brain--or even to come up with seriously considered theories of how this might be so; and consciousness is clearly capable of exerting downward causation on the structure of the brain--everything from suicide and drug use (which affects the biochemical makeup and functioning of the brain) to more subtle effects such as emotion (changing blood flow patterns) and meditation (which, over time, evidence suggests can fundamentally re-wire certain brain hardware).
Contrast strongly emergent human consciousness with "weak" emergence--the many social and natural phenomena that, while being theoretically reducible to the laws governing individual components, and capable of modeling and simulation, are practically too complex to understand in any way other than by modeling and simulation. The human brain/consciousness pairing is particularly intriguing in the study of strong emergence because 1) despite many, many examples of "emergence," the consciousness is the only clear example of "strong" emergence that I'm aware of; 2) it is exceptionally well studied; and 3) it is something of direct interest and access to all of us.
What characteristics of the brain appear to facilitate strong emergence? In "Social Emergence," Keith Sawyer notes that:
Complexity theorists have discovered that emergence is more likely to be found in systems in which (1) many components interact in densely connected networks, (2) global system functions cannot be localized to any one subset of components but rather are distributed throughout the entire system, (3) the overall system cannot be decomposed into subsystems and these into smaller sub-subsystems in any meaningful fashion, (4) and the components interact using a complex and sophisticated language.
P. 4-5. The human brain arguably exhibits all of these attributes, but is particularly notable for the first attribute--many components interact in densely connected networks. Another notable sociologist and systems theorist, Talcot Parsons, noted that decomposable systems--that is, systems comprised of functional modules that only interact at specific points and in specific ways--are far less likely to exhibit emergence than are non-decomposable systems. While neurology and psychology suggests that certain brain functions are localizable to what are arguably functional modules, the phenomenon of consciousness (or, as some suggest, related set of phenomena) does not seem to be so localizable.
I suggest that this notion of "localizable" is better viewed as a matter of "non-hierarchal." Where components are organized into hierarchal structures, they are almost by default localizable, and this hierarchal nature may provide insights as to why this matters--in hierarchy, the "base of the pyramid" does not communicate freely and frequently with the base of other pyramids, but rather this communication is channeled and mediated through the hierarchal structure itself.
I also think that pattern of connections between neurons in the brain is critical--rather than a "lattice" or "crystal" structure where neurons are routinely connected to only those physically proximate neurons, the brains neurons tend make relatively distant and non-uniform patterns of connection. I've discussed this type of connectivity elsewhere as an optimal configuration of "small worlds networks," and I think it plays an important role in consciousness because it amplifies the connective and communicative power of already dense networks.
Based on this foundation, it seems that the key structural attribute of the human brain is dense networks of weak (more than just physically proximate) connections with very little or no hierarchal structure noticeable in the operation of individual neurons or their pattern of connectivity. Out of this structure, human consciousness emerges, apparently irreducible to the action of the neurons themselves, yet able to influence the structure of those neurons (both on a micro-level of memories, personalities, etc., and on a macro-level of biofeedback in various forms).
Of course, without a clear understanding of how and why strong emergence occurs (something that, by the very nature of a phenomenon being strongly emergent may be unknowable?), we are left with the leap from "these properties are present in a system that produces strong emergence" to "therefore the presence of these properties in a system causes strongly emergent phenomena." While we should recognize this logical leap and not attempt to sweep it under the rug, we would do well to also recognize that this is very much the same leap that we always take when reaching conclusions as to causation. As Scottish philosopher David Hume pointed out plainly, at some point we always make the unsupported leap from (simplified) "this happens after that happened" to "this happens because that happened."
With only one good example to work with (human brain --> consciousness), I'm not yet ready to state that it is the structure of the brain that creates consciousness, or the corollary (and what I'm really interested in) that replicating these structural attributes elsewhere will similarly produce strongly emergent phenomena supervenient on that structure. This is, however, my working hypothesis--I'd love to hear thoughts on other examples that tend to support or refute it. In the next post, I will conclude this series (at least for now) with the application of this hypothesis to building a sustainable social structure.
Readers may also find my litigation checklist of interest.