Jonathan Birch has an interesting paper in Noûs: The search for invertebrate consciousness. Birch notes that there is no consensus on whether any invertebrates are conscious, and no agreement on a methodology for establishing whether they are.
He starts off assessing the difficulties of applying many human centric theories, such as global workspace, which don’t have a floor for how sophisticated the mechanisms need to be for consciousness. (For global workspace: which specialty systems are necessary for the workspace, and how many are required?) On the other hand, many theories from animal research, such as Merker’s midbrain centered one, aren’t really supported by evidence from human studies.
He also sees problems with totally theory-neutral approaches. Researchers often assume behavior associated with certain experiences in humans are the same in other species. But often these behaviors are automatic and don’t require the experience. An example is learning avoidance behavior, which in humans is typically accompanied by unpleasant experience, but similar behavior can be observed in a rat spinal cord that’s been disconnected from its brain.
To thread this needle, Birch advocates an approach he calls “theory-light”. He sees this approach as being based on a particular hypothesis:
The hypothesis I have in mind I call the facilitation hypothesis. The motivating idea is that phenomenal consciousness does something for cognition, given the actual laws of nature, but precisely what it does is a question to which we do not yet have definitive answers.
…The claim is that, holding all else fixed (e.g. the stimulus, the difficulty of the task), a cluster of cognitive abilities is facilitated when the stimulus is perceived consciously.
In other words, consciousness provides benefits. It isn’t an epiphenomenon, a side effect that has no causal effects for the organism. This means that a way to establish consciousness in an animal is to examine its capabilities. (This seems resonant with Daniel Dennett’s hard question strategy.)
Birch is interested in direct ties to human experience, so he’s looking for capabilities associated in humans with phenomenal awareness. The primary capability in humans, and the gold standard for evidence about conscious experience, is verbal report. Of course, that’s only available in humans. However, there are others that tend to only be possible in situations where verbal report is also possible. A few candidates that Birch identifies:
- Trace conditioning: in which an organism is able to learn an association between two sensory stimuli separated by a time interval, such as learning that a tone is associated with a puff of air in the eye one second later.
- Rapid reversal learning: in which the animal, once it has learned about an association between two stimuli, is able to quickly adapt when one of the stimuli ceases. This would be a measure of how quickly Pavlov’s dogs adapt when the bell no longer signals the food treat.
- Cross-modal learning: learning associations across sensory modalities, such as associating a visual stimuli with an auditory one (i.e. the bark of a dog with the sight of one).
Birch admits that any one of these might be able to happen unconsciously, but the more that are present, the stronger the evidence for phenomenal experience. He goes on to examine some of the evidence for these capabilities in bees, and comes to the conclusion there is limited, but not yet conclusive evidence, for bee consciousness.
This approach is similar to the ones taken by Todd Feinberg and Jon Mallatt in The Ancient Origins of Consciousness, who used global operant learning, value trade-off behaviors, and other capabilities to establish affective consciousness (sentience), as well as the approach by Simona Ginsburg and Eva Jablonka in The Evolution of the Sensitive Soul, which focused on unlimited associative learning. (Mallatt and Jablonka are actually acknowledged as reviewers at the end of the paper.)
So the overall approach here isn’t really new. But Birch’s set of capabilities seem to come from a broader net. He seems to be identifying cases of classical learning (sensory-sensory associations), but in a more sophisticated form. They may be easier to test for than operant learning, which requires an action component.
That said, Birch’s approach strikes me as typically binary in its thinking: either the animal is conscious or it’s not. This makes his approach perhaps more theory laden than he thinks. It’s hard to look at consciousness in something like a bee without holding some particular definition of “consciousness.” We know a bee’s information processing is going to be some subset of the human version. Whether any particular subset is both necessary and sufficient for consciousness isn’t a fact of the matter. (At least until someone conclusively discovers a “consciousness field” or some other objective basis for phenomenal consciousness.)
Birch argues that we don’t need more theory, nor more “undirected data gathering”, but investigation along his theory-light strategy. Given the point above, I’m not sure that’s true. I think the most productive thing we can do is learn as much about the capabilities of bees and other invertebrates as possible, and then with those established, discuss what kind of consciousness they have.
But maybe I’m missing something?