Sean Carroll’s latest episode of his podcast, Mindscape, features an interview with neuroscientist Malcom MacIver, one that is well worth checking out for anyone interested in consciousness.
Consciousness has many aspects, from experience to wakefulness to self-awareness. One aspect is imagination: our minds can conjure up multiple hypothetical futures to help us decide which choices we should make. Where did that ability come from? Today’s guest, Malcolm MacIver, pinpoints an important transition in the evolution of consciousness to when fish first climbed on to land, and could suddenly see much farther, which in turn made it advantageous to plan further in advance. If this idea is true, it might help us understand some of the abilities and limitations of our cognitive capacities, with potentially important ramifications for our future as a species.
The episode is about 80 minutes long. If your time is limited, there’s a transcript at the linked page.
MacIver largely equates imagination, the ability to plan, to think, to remember episodic memories and to simulate possible courses of action, with consciousness. I can see where he’s coming from. I’ve toyed with that idea myself. (I don’t use the word “imagination” in the linked post, but that’s what’s being discussed.)
But while I think imagination is an important component of consciousness, meeting a lot of the attributes many of us intuitively associate with it, it doesn’t appear to be the whole show. This is one reason why I often talk about a hierarchy of consciousness:
- Reflexes: survival circuits, primal instinctive reactions to stimuli
- Perception: predictive models of the environment based on sensory input, increasing the scope of what the reflexes react to
- Attention: prioritization of what the reflexes react to
- Imagination / sentience: simulations of possible courses of action based on reflexive reactions, decoupling the reflexes so that they become affective feelings
- Metacognitive self awareness / symbolic thought
The consciousness of a healthy mature human contains this entire hierarchy. Most vertebrates have 1-4, although as MacIver discusses, the imagination of fish is very limited, usually only providing a second or two of advance planning. Land animals have more, although most can only plan a few minutes into their future. The more intelligent mammals and birds can plan further. But to plan weeks, months, or years in the future seems to require the volitional symbolic thought that only humans seem to possess.
But many of us, if presented with an animal who only has 1-3, will still regard it as conscious to at least some degree. This is particularly true with humans who, due to brain pathologies, may lose 4 and 5. The fact that they are still aware of their environment and can respond habitually or reflexively to things still triggers most people’s intuition of consciousness.
Which view is right? Which layers must be present for consciousness? I don’t think there’s a fact of the matter answer. Unless of course I’m missing something?
h/t James of Seattle