I often say that consciousness lies in the eye of the beholder, a notion that many dislike and often push back against. To be clear, I do think that for any precise definition of “consciousness”, there is a fact of the matter about whether it exists and what has it. Many respond by offering up their own definition, which is fine, but it doesn’t address the main problem, that no definition of consciousness commands a consensus.
Note that I emphasized “precise” above, because definitions like “subjective experience”, “something it is like”, “the feeling of life itself”, and similar quick takes are pretty vague. That vagueness allows an illusion of agreement, but there are a wide variety of more precise conceptions that could underlie each of them, and drilling down into those conceptions tend to expose disagreements.
A few years ago, in a post about panpsychism, I developed a hierarchy of consciousness definitions, which are occasionally pulled out when a discussion comes up about whether a particular species or system is conscious. It’s not in any way meant to be a definition itself, or another theory of consciousness, just a pedagogical tool to quickly recognize the landscape. And one to emphasize that consciousness isn’t a binary thing, a matter of a light being on or not.
That said, it is inherently monist, as in not dualist. It also excludes forms of physical dualism which, if ever found to be true, might establish some definite boundary for is or isn’t conscious.
Here’s the current version:
- Matter: a system that is part of the environment, is affected by it, and affects it.
- Reflexes and fixed action patterns: automatic reactions to stimuli in service of innate goals (either evolved or designed).
- Perception: predictive models of the environment built from distance senses, increasing the scope in space of what the reflexes are reacting to. Bottom up attention begins here.
- Habits: Selection of which reflexes to allow or inhibit based on accidentally learned associations of stimuli with reflexive reactions.
- Volition: Selection of which reflexes to allow or inhibit based on observationally learned predictions of reflexive reactions, extending the scope of reactions in time as well as space. Top down attention may begin here.
- Deliberative imagination: sensory-action scenarios, episodic memory, which enhance 5, extending the reactions much further in both time and space.
- Introspection: deep recursive metacognition enabling mental-self awareness, symbolic thought, and exponentially increasing the scope of the reactions.
Panpsychists will associate consciousness with 1. Biopsychists will insist that the goals in 2 must be evolved ones, although some may not see consciousness itself arriving until higher up in the hierarchy. Someone looking for minimal or primary consciousness may find it either at 3, 4, or 5, depending on their precise views. John Locke’s definition of consciousness, as knowledge of what passes in one’s own mind, requires 7.
All biological life, including plants and unicellular organisms, have 2, as well as any automated technological systems. 3 comes in for any system with distance senses, such as sight or hearing. 4 seems to exist in many arthropods, as well in fish and other pre-mammalian vertebrates. 5 may exist in some of those species, but seems most evident in mammals and birds. Which species have 6 is pretty controversial, with some biologists seeing it widespread in mammals and birds, but others restricting it to certain highly intelligent species. 7, at least for now, seems unique to humans (mentally complete humans, which may not include infants and brain injured individuals).
With life, everything starts with the reflexes and fixed action patterns, that is, automatic reactions. Everything above that expands the scope of what those automatic reactions are responding to. In my view, consciousness can be seen as a form of spatiotemporal intelligence, and all intelligence could be viewed as the capability to make predictions, with higher degrees of intelligence equaling how far into space and time the system can make useful predictions.
In previous versions, I’ve thrown around terms like “affect” and “sentience”, but over time it’s become clear to me that was somewhat begging the question. So this version is mute on exactly when those qualities arrive, leaving it to you to work out for yourself when you think they do, as I largely did for body-self awareness in previous versions. My view is that there isn’t a strict fact of the matter, although I’ll admit that somewhere around 4 or 5 my intuition of a fellow conscious entity starts to emerge.
It’s worth noting that a hierarchy isn’t the only way to look at this. Jonathan Birch and colleagues developed a dimensions of animal consciousness approach that I like. Each of the dimensions can be present in varying degrees. Some of the items above, reflexes and perceptions, show up as dimensions. Other dimensions such as temporality and selfhood are more implied as growing in each layer. I have to admit that my hierarchy largely assumes another dimension: unity. And it’s not clear how accurate that is for many species, particularly cephalopods.
All of which is to say, that talking about whether many systems are or aren’t conscious is a somewhat meaningless exercise. It’s really a discussion about how much like us those systems are. In fact, if someone pointed a gun to my head and demanded I provide a succinct definition of consciousness, that would likely be it: like us. It’s the only one that I know that captures what every other version seems to have in common, and it also acknowledges how amorphous the concept actually is.
So, other humans are very much like us. Other great apes are more like us than small monkeys, which are more like us that dogs, cats, or birds, which are in turn more like us than frogs, fish, or crabs. And all of them seem much more like us than anything technological, at least for now. Cephalopods are an interesting case, showing that some systems with very different evolutionary lineages can still trigger our intuition that there’s something like us there.
Unless of course, I’m missing something. What do you think? Is this hierarchy useful? Would it be better to just focus on Birch’s dimensions? What do you think of my succinct definition?