Back in May, I shared a paper that made a blistering attack on the integrated information theory (IIT) of consciousness. A major point of IIT is that a specific causal structure is necessary to generate phenomenal experience, namely a feedback or recurrent neural network, that is, a neural network with structural loops. To be clear, IIT asserts that this causal structure must be physical. Implementing it in a software neural network wouldn’t be sufficient.
However, the unfolding paper mathematically demonstrated that any output that can be produced from a recurrent network, can also be produced from an equivalent “unfolded” feed forward network.
If so, there might be no observable differences in the behavior between a system IIT predicts is conscious vs a computationally identical but unfolded one that IIT predicted would not be conscious. In other words, IIT would be labeling the feed forward system a philosophical zombie (a behavioral one). Zombies are untestable, making this aspect of IIT untestable, leading the authors to label IIT as unscientific.
Now, a group of IIT researchers have produced a response paper. One of the response authors shared what appears to be a draft version. (Which means this link might go dead at some point. I’ll try to remember to update it when the actual paper gets published.)
The response authors start by labeling the stance of the unfolding paper as one of methodological behaviorism, one they say advocates studying the external behavior of subjects and basing theories entirely on that. Their stance, on the other hand, depends on “the link – known to each of us by first-hand experience – between conscious experience and behavioral reports,” and builds theories based on conscious experience.
There is some discussion about assessing the consciousness of a human compared to a black box system of some kind. They think it’s fair game to take what is known about the human’s internal structure to privilege it in this assessment. This seems like an implicit argument against the Turing test.
The response authors go on to assert that the analysis of the unfolding paper was done within the behaviorist and functionalist mindset. They take the stated conclusions from that paper and amend language to them, adding in effect: “except for consciousness.”
“(P3): Two systems that have identical input-output functions cannot be distinguished by any experiment that relies on a physical measurement (other than a measurement of brain activity itself or of other internal workings of the system).”
P3’ “Two systems that have identical input-output functions (except where conscious experience is concerned) cannot be distinguished by any experiment that purely relies on input-output measurements. We can distinguish these two systems, however, by understanding the internal working of the respective systems, through the systematic investigation of the links between reports about consciousness and physical stimulations/measurements of the internal mechanisms.”
It’s worth noting that their proposed methods still crucially depend on reports, which is just a form of output measurement. In other words, they’re still doing what the unfolding authors say is the only way to proceed. They’re just implicitly asserting that the specific internal structure details will make a difference in those measurements.
But if they turn out to be wrong about that, and the output of some system is the same irrespective of specific internal structure, then under IIT, they’d be forced to regard that system as a zombie, which again brings us to the point that the unfolding authors made. We still only have the output of the system as evidence. We can only use internal structures as an indicator if they happen to match that of another system whose behavior has already convinced us of its consciousness.
Interestingly, the response authors could have attacked this at a computational level, asserting that another physical causal structure that is identical in terms of inputs and outputs might not be identical in terms of efficiency or performance. It might be that IIT is wrong in principle but right in terms of effectiveness. But that would have meant engaging the argument on functional grounds.
Finally, the response authors make the case that just because IIT makes some untestable predictions is no reason to label it unscientific. Many scientific theories make such predictions. The question is whether they make other predictions that actually are testable. Theories, they point out, should be judged on their testable predictions.
I actually felt like this was the strongest part of their argument. In retrospect, I think the unfolding authors overstated the case against IIT. The predictions they discussed are untestable, but not all of IIT’s predictions are.
On the other hand, the response to the specific issues raised didn’t strike me as successful. And theories should also be judged on whether they’re the simplest explanation for the evidence.
Admittedly, this comes from the perspective of a functionalist who finds little theoretical merit in IIT. But maybe I’m missing something?