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Evolution of consciousness
M. Tintner
Friday, 25 September 2009 10:34 UTC
I’ve just been discussing the evolution of consciousness with a friend.
My assumption is that the “surround movie screen” which is (I agree with Hans) the principal content of human consciousness, has steadily evolved through animals – from v. early on in evolution. No doubt, the screen has become steadily more focussed, detailed, coloured, and multi-sensory. But, I assume, there has had to be some kind of “screen” (a somewhat distorted/flattened metaphor for the real thing) – because that screen provides an essential, integrated way to map the world around an animal, and view how things fit together and relate.
My friend, OTOH, questions whether this screen evolved before mammals:
“vertebrate animals which don’t have the visual cortex [meaning non-mammals] have an optic tectum as their primary visual center. The optic tectum responds almost exclusively to moving objects [ie, no one to my knowledge has shown much response to fixed objects]. Eg, frogs will supposedly starve to death surrounded by dozens of dead flys.
Further, the analogue of the optic tectum still exists in mammals, and is called the superior colliculus. SC cells respond mainly to motion. Furthermore, humans who have damaged visual cortices can still respond to objects as long as they are moving.
This last is called “blind sight”. They can respond accurately to moving objects, but they do not “consciously” see. They claim to be blind, and cannot “see” the objects. IOW, to not be able to view the “screen” you’ve been talking about.
What this boils down to is that animals without cortex do not have your screen, or otherwise what we think of as “conscious sight”. "
I would point out in return, that it is hard to see how lower animals can navigate the world as they do, moving between objects, (and having a moving POV of objects) – and that includes navigating mazes – if they don’t have some kind of screen/map of the immediate world.
My assumption is that even a blind worm will not just experienced fragmented, disparate, sensations of objects, for example, but will need to integrate them into tactile “maps” in order to manoeuver the objects as skillfully as it does, and drag them considerable distances to its burrow.
I’d be v. interested to hear the views of the group on all this, and esp. on what is known scientifically – and what attempts have been made to chart the evolution of consciousness in the above sense.
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Well Graeme, a sea anemone, if you’ve seen some of those movies of evolution, can wait while a fish approaches, and then pounce and grab it at the appropriate moment, and consume it – all with just a neural net and no brain.
Obviously, the task of a true evolutionary psychology that deals with the whole evolution of mind – & not just the human exceptionalist variety we currently have – is to explain how mind evolved into the brain – became centralised in the first place.
My v. limited understanding of the neurology here suggests that there are vast amounts about how brains and nervous systems reflect and represent the world that we do not understand – and that even v. primitive organisms have much greater powers here with apparently v. limited neural resources, than we can begin to account for.
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There is no mystery of why brains developed, as far as I know, they weren’t needed until multicellular animals became motile, and then they were needed to guide the animal while it relocated.
Just because a sea anemone waits until just the right moment to pounce, on its prey, (More like sting its prey to paralyse it, and then capture it) doesn’t mean that it is aware that it is doing such. The mechanism needed is a threshold trigger that somehow coordinates the multiple stingers, and the manipulatable fringe of tentacle like protrusions, each of which can have its own wired logic that causes it to bring the fish closer so that it can be digested.
The reason why the Anemone has a distributed network of neurons, and the C-elegans doesn’t is because worms move in one direction or another, and so they need a guidance mechanism to direct their movements. So C-elegans will have the precursor to a real brain. The anemone is permanently glued to the coral reef or rock, it is attached to, and only storms can tear it loose and move it from one location to another. It doesn’t need a brain so much as an instinctive ability to feed itself.
I think that there is a tendency to romanticize intelligence of any sort, and imbue it with labels of consciousness built into the human mind, and this is what you are experiencing when you assume that the anemone is conscious.
By the way I am not an Evolutionary Biologist my interest is in consciousness itself, and how the evolution of the brain decided the nature of the architecture of the brain, which in turn, influences what the brain can do, and how it does it.
The brains of mammals have distinct Allocortical Tissues, that I think do the job of implicit memory. Obviously the cortex layered structure of these allocortical tissues is not the same as the drosophila or fruit fly, if only because its head is too small for the same type of cortex to exist. But I would be remiss if I didn’t state that I thought there was a missing layer of psychology between neuropsych and organic Psychology. We need to understand a bit better how homogeneous networks of neurons work before we will properly understand if the few memory cells in the drosophila or snail memory are implicit, or not.
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Graeme,
Thanks for an interesting, informative reply. It raises further issues. You say a brain is needed for “motility”. Well, this serves to raise a further useful distinction. The anemone is clearly “motile” – it’s moving its tentatacles in a coordinated way. So are infants motile at first as they try to coordinate first head, then arm, then torso movements and so on – long before they can eventually crawl around. I think you’re really referring to “mobility” – or “locomotion.”
I’d also like to tease out further distinctions raised by your idea of “awareness” – wh. seems to equal something like reflective recall of an agent’s actions, or even “capacity to self-describe”.
I wonder whether the anemone doesn’t have a kind of consciousness – we are conscious of our movements, but we don’t have “reflective recall” of most of them, or the capacity to describe them – for example, the way we ride a bike. They come under, arguably, something like Polanyi’s “tacit knowledge”.
You may be right about an anemone’s lack of “consciousness” – but, as things stand, I suggest, you may also be wrong. We just don’t know enough to conclude – wh. is partly the point of my starting this thread.
If it’s true, as you say, that the anemone stings its prey – (as I said, I’m pretty ignorant here) – then that indicates a certain complexity of operations and problemsolving – and, just possibly, body coordination – that may well be still considerably beyond present robotics.
I think what we mainly have – and should have – here are questions, rather than conclusions.
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I still think you have a romantic view of what neurons can do.
Ok, so maybe mobility was the word I wanted to use. The Sea anemone is glued to the rock, it doesn’t move anywhere on its own, so it doesn’t need to navigate. As a result there is no need for it to specialize a brain. It can do well with radial symmetry. C-eleganz on the other hand is a worm, it doesn’t need consciousness because it is just squirming through the loose detrius on the sea floor (I assume). It does need some instinctual learning in order to be able to lead with its sensory cluster, and in order to squirm in a way that moves it forward, and it needs some drives, such as a drive to move towards food, and away from detrius that tastes bad. But why would you assume that it needs consciousness? or that consciousness would be available to it?
I think you are mistaking consciousness for vitality.
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On Reflection versus Reflective Recall.
Reflection in the terms I was using, is a data direction term, not a term describing introspection. Reflective Recall, is more like Introspection.
The differences are significant, in one we assume that the data loops back into the datastream, allowing the results to be processed, after the original processing has been completed, and in the other we assume some control over the choice of which elements are reflected upon, by selection from the memory.
I can assure you that neither C-elegans or the Sea Anemone have the capacity to reflect upon memories, if only because that capacity requires a larger brain than C-elegans and a more integrated brain than the sea anemone could possibly have.
In fact, we are not entirely sure that C-elegans has even a rudimentary implicit memory apparatus. In all likelihood it doesn’t, since all that is required for the level of cognition I have suggested is some basic ganglia.
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