Science Interviews


Thu, 25th Sep 2014

What is life and where did it come from?

Nick Lane, UCL

Listen Now    Download as mp3 from the show Alien Hunters: The Search for ET

This week, weíre looking for life beyond Earth: is there anybody out there? Remarkably, Still Lifeweíre making progress in answering that question. In the last few years, weíve discovered that our galaxy is teeming with alien planets but the big question remains - do any of them harbour life? Coming up, how do we define life and how did it begin; what can we tell about planets thousands of light years away and how many alien civilisations they might be home to? Now to many people, astrobiology means the hunt for alien life, but a big part of this is understanding what life actually is, and whatís needed for it to exist. 

Everywhere we look on earth, thereís life in an endless variety of shapes and sizes- from microbes to elephants. But how do we define it? What is life and how is it different from non-life?  Nick Lane is a biochemist and he spoke to Chris Smith about the origins of life.

 Chris - So, how do we tell whatís alive like a mouse from a brick? Because chemically theyíre both made of very similar things.

Nick - It is notoriously difficult to do and actually, I think itís almost pointless to try to define life. I mean, thereís hundreds of definitions of life out there and theyíre all wrong in one way or another. And the problem is that life is really a continuum from a non-living state to a living state and thereís all kinds of intermediate stages. So, is a virus alive or not is a question which is often discussed. Itís really what life does rather than what it is, and in all these cases, life is making copies of itself and itís using the environment to do so. So, one of the problems with most attempts to define life is that it excludes the environment. All life parasitizes the environment in one way or another. Plants do, they require sunlight, they require carbon dioxide, they require water, and so on, thatís all they require. We parasitize the environment a lot more. We go around eating plants and so on. But essentially, all life is parasitizing an environment which is providing it with its energy needs to make copies of itself, so I think youíd say there are about six different things a cell requires. It requires a carbon source to make more copies of itself, it requires energy to bind things together, to make polymers and to produce more cells, it requires excretion, youíve got to get rid of the waste products and the end products to drive reactions in a forward direction. There has to be some form of compartmentalization, a cell-like structure that makes the insides different from the outside. There have to be catalysts, the beginnings of biochemical reactions, and then, there has to be some form of replication. Now I think those are the six properties of life that we really need to look for.

Chris - You said that there has to be a carbon source. To what extent is the life we see here on Earth so unique to this environment that youíre not going to find it anywhere else or do you think if another planet Earth-like environment exists out there that life would take exactly the same pathway of evolution that it has here and we will be looking at our mirror image out there, somewhere.

Nick - I think thatís actually a good argument to say that life could end up, at least at the bacterial level, remarkably similar. I mean, thereís a strong argument to say that carbon is really better than anything else. Itís much better than silicon, for example, at forming, you know, complex bonds between molecules and itís also available. You know, carbon is far more available in the universe than silicon and also there are gaseous carbon oxides, carbon dioxides, and so on. Itís like a Lego brick, whereas silicon oxides are, you know, sands and so on, you canít really boot-strap yourself up from the ground with sand. You canít build on sand.

Chris - So, youíre sort of saying that because the rules of physics and chemistry are universal throughout the universe, therefore, exactly the same constraints will exist wherever you live Ė Milky way or even the Andromeda galaxy and therefore, youíre gonnaí end up following the same sorts of pathways.

Nick - I think, yes, itís possible. We can conceive that life couldíve operated in different ways but if you think about the probability of finding life, carbon, water, the kind of rocks that are required for hydrothermal systems and so on. They are all very common, so the kind of life that we have here is likely to be the kind of life that we find elsewhere as well.

Chris - The Earthís four and a half billion years old, so how long after the Earth formed, did life first pop up?

Nick - Well, we donít really know. Thereís a lot of arguments about it, a kind of glib answer would be about four billion years ago. There are fractionated isotopes of carbon and so on in ancient rock from about 3.9 billion years ago. Thereís a lot of debate about whether that signifies life or not, but I think most people think on balance, it probably does.

Chris - Where do you think that life came from? What sorts of theories are out there to explain how life arose? Did it arrive de novo, in other words, from scratch here or is it possible that it could have had some kind of injection of some processes from, say, outer space. 

Nick - Well, we know for sure that thereíve been plenty of organic molecules delivered from space on meteorites, thereís no question about that. Whether that prompted life on Earth in some way, conceptually what it does really is stock a soup, and so conceptually, itís not really any different to say the Miller-Urey experiment from 50-60 years ago, showing that lightning and UV radiation and so on, can also produce organic molecules, so can hydrothermal vent systems. Itís actually remarkably easy in some ways to produce organic molecules and remarkably difficult to get beyond a soup.

Chris - So, would you be in favor then of the idea that life just spontaneously started, or do think that actually that there is credence to this idea that there could have been life coming from elsewhere, maybe intact life coming from elsewhere in the universe.

Nick - Thereís no evidence to suggest that it did, and actually I think itís a pointless theory in the sense that if it did come from somewhere else, well we still donít know any more about how life started elsewhere. I think weíll never know exactly how life started on Earth but what we can know, what are the principles that lead to the origin of life from a non-living environment, and thatís what weíre looking for in trying to understand the origin of life here. And panspermia, the delivery of life from space, it just moves the problem somewhere else so itís pointless.


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The essence of life seems to be a local reversal of mesoscopic entropy.

Where did it come from? Why would anyone think it came from anywhere else? The conditions for the continuation of life seem to be fairly narrow, yet widely available on the surface of this planet, so evolution is most likely to have begun here. The question is whether it started first on the hard surface or (more likely in my uninformed opinion) on the sea bed. alancalverd, Tue, 30th Sep 2014

Alan, I have to respectfully disagree.

There are many spontaneous local reversals of entropy, including crystallization, condensation, accretion (even on planet scale). There are also many patterns that self propagate. There's more to it than that.

Also, a tortoise in the galapagos could be forgiven for thinking that all life was particularly well evolved for life on his rock, and therefore must have begun there. I'm not saying that I know of any evidence that we originated elsewhere, but the possibility cannot be dismissed just because it looks like life is too well adapted, and requires conditions found only on Earth (as far as we know for certain so far). chiralSPO, Tue, 30th Sep 2014

Someday we'll all have to sit down and decide when a definition of the terms that we use here is required. Lol!

Tell me something, Alan. What in the world is mesoscopic entropy and why should it have anything to do with life? I myself tend to believe there is a relation to energy and life but I've never had the time to sit down and seriously think about it.

I myself think that life started off as something quite different than what we think of when we think of life and then the method of propagating  change worked itself and then evolution. PmbPhy, Wed, 1st Oct 2014

In this context this is known as negative entropy. Schrodinger wrote a book called What is Life? in 1944 which has something to do with entropy. Not sure what though. See PmbPhy, Wed, 1st Oct 2014

It's misleading to think of entropy simply as disorder. It's really about probability. So a crystal, whilst being highly ordered, is in a lower energy state than a liquid of the same material and thus, at any temperature below its melting point, more probable.

However we look at living things, they are extremely improbable and locally out of equilibrium with their environment. But they do die, exhale, and generally cause chaos. Ergo mesoscopically and locally (both in space and time) negatively entropic even though their components are microscopically obeying all the usual Gibbs equations. alancalverd, Wed, 1st Oct 2014

Life is a vague term.

From the point of view of how it works, the biological species could be considered automatic robots of some sorts executing a code in-scripted in their DNA, i.e., a biological individual might be a mecanical-hydrodynaqmical-biochemical-electroddynamical robot composed of trillions of cellular sized micro-robots.

However, what is striking about biological species is that their brain create an internal representation of the world accesible only from 1st person perspective of the raw sensation of something. It seems to me that this internal representation of things put together by our brain   has to be related to the capacity of biological species to be/have conscious (or self-conscious).

The most important aspect regarding biological species sufficiently evolved to have nervous system is their consciousness (and self-consciousness for most evolved species). flr, Wed, 1st Oct 2014

I disagree.

Its actually for this reason that think that life is a well defined term in that its automata, i.e. little organic robots. PmbPhy, Wed, 1st Oct 2014

OK, if life is not a vague term, please define it! alancalverd, Wed, 1st Oct 2014

This type of query is a common error in both math and science. It assumes that just because something is not vague then there must be a clear definition to it.

A perfect example from math is the term set. People try to define a set as a collection of objects but all that does is require us to define the term "collection" thus putting us back in the same place that we started from. PmbPhy, Wed, 1st Oct 2014

Wouldn't life have a special meaning because it can lead to conscious creatures?

Without self-aware creature how will be universe in 10^1000 (which might consists mainly in a soup of photons) be more interesting that today's universe that is highly structured, since the same law of nature apply anyway.? flr, Thu, 2nd Oct 2014

So I'll answer my own question. Life is the common property of living things. Now that remains undefined but at least it refers to something that can be defined since we can define the characteristic actions of a living thing, or we can list all things that we call living.

You might argue that there are still unresolved borders: is a virus alive? Not really a problem because the initial categorisation was only for convenience, as with species. We can look at another abstract noun: beauty. Yes, it's the common property of beautiful things, and we can list a whole lot of people, animals, sunsets and artefacts that everyone agrees as beautiful, but there will be unresolved borders.

So if you want to get mathematical, life is the characteristic of a fuzzy set. And I won't define fuzzy or set!  alancalverd, Sun, 5th Oct 2014

This might add some thoughts to the mix.

ďSelf-replication is a capacity common to every species of living thing, and simple physical intuition dictates that such a process must invariably be fueled by the production of entropy.Ē
Bill S, Tue, 7th Oct 2014

I detect a genuine brilliance in that statement alan, but if I may, I would like to add one small addition.

"Life is the characteristic of a fuzzy set that makes the futile attempt at resisting entropy."

Ethos_, Tue, 7th Oct 2014

....except for the mule, hybrid roses, GM rice, several humans.... The problem is that "species" is undefined but generally (but not exclusively) used to retrospectively label a group that has reasonably successfully reproduced. Sexual reproduction pretty well guarantees nonreplication, and if exact replication were the order of living things, there would have been no evolution. The best we can say in this line is that some living things beget more living things, which isn't much of a definition.    alancalverd, Wed, 8th Oct 2014

How about consciousness. If we would find a crystal able to have a conversation with us, would it be 'alive'? yor_on, Wed, 8th Oct 2014

If I was allowed to make one rule for this and every discussion forum, for all time, it would be to remove any post that uses the word "consciousness" without defining it.

I have yet to enjoy a conversation with a slug or the lettuce it is eating, yet to the best of my knowledge they are both alive. On the other hand, mediums and churchgoers claim to have conversations with people who are dead, or entities that never existed. alancalverd, Wed, 8th Oct 2014

heh, slightly arid (as in dry that is :) response there my dear Alan.
You do have a point, and i think I agree, although that also depends on what we mean by consciousness? If we now would include the slug? what is 'self aware'? Is that a acceptable definition of consciousness? Is that just me having a problem with defining it as carbon based? then again, a crystal might not be the best definition if so :)
Nomenclature sux at times. yor_on, Thu, 9th Oct 2014

There are very simple machines that are self-aware but far from alive. My present car engine checks its state of health and won't let me drive too fast if it isn't feeling completely happy. I have disconnected the bit that stops me driving into things (reversing sonar that can activate the brake) but the gadget that stops the wheels spinning or locking seems to be quite handy, as are the automatic windscreen wipers. In short, the car knows how to protect itself and its occupants from major trauma, and is aware of its relationship with its rapidly changing environment. Slugs are even more clever, though a bit short of defence mechanisms.  alancalverd, Thu, 9th Oct 2014

OK define unconsciousness. jeffreyH, Thu, 9th Oct 2014

It's those annoying intervals between sleeps. Bill S, Thu, 9th Oct 2014

I believe this is the key question.
Is consciousness a result of the physical processes taking place in the brain? Can consciousness be fully explained by what happens in brain?
Neuroscience identified neuronal connections for certain basic conscious processes, however it cannot explain why passing of ions/e- through a certain neuronal pathway result in subjective experience of one particular person. 

Many critical biological processes are controlled by brain at subconscious level (such as heart rate, breathing, sugar level in blood, etc).
Why then haven't nature produced only philosophical zombies?

It could also be a smart computer program, in which case does not need to be 'alive'.
How could we know if it has conscious or it is just a smart computer code/bot?


flr, Fri, 10th Oct 2014

That's one interpretations of what self aware could be. Another might be when you're aware about yourself, think I saw some writing that monkeys seems to know that they were looking at themselves, when looking in a mirror. Some other animals just don't make that connection, So let's go get back to that crystal again (ahem, not carbon based though) showing it a mirror :)

the darn thin should be deciding if it notice though? I've seen it said somewhere that crystals are notoriously bad in showing their emotions. Still, even so it might be self aware. yor_on, Fri, 10th Oct 2014

And yeah, a Turing machine of sorts. But if it evolved naturally, wouldn't that be intelligence? yor_on, Fri, 10th Oct 2014

there is something it is like to be in that state from a subjective or first-person point of view. flr, Fri, 10th Oct 2014

Tell us what it is, and we'll find out how it works. alancalverd, Fri, 10th Oct 2014

There may be a fundamental difference between Turning machine and awareness.

A Turning machine can only solve problems that can be put in algorithm. Algorithm means automatic, i.e. a pre-established way to traverse a tree; like a robot.  A turning machine cannot solve by itself the halting problem, while our mind instantaneously can.

I believe Rodger Penrose got this right: there is something fundamentally non-computable in the way our mind works.

It seems to me that what evolved naturally it is more than a Turning machine. It is something that could sense that from a subjective 1st person view that something it is like to be in that particular state. Turning machines cannot do that: to sense that there is something it is like to be in that particular state. 

flr, Fri, 10th Oct 2014

As for "Is consciousness a result of the physical processes taking place in the brain? Can consciousness be fully explained by what happens in brain?"

I like the idea of emergences myself. Seen it defined as what can not be back tracked to its constituents solely. The emergent new pattern have a complexity of its own. Defined so thoughts are an emergence. It makes the idea of 'consciousness' versus entropy really interesting.

It's not so that you can have one without the other. You need entropy, you need causality, you need a arrow to gain this new 'emergence' of thoughts. If we on the other hand speak of 'superpositions' I also understands it as we can assume a 'universal superposition', describing the whole universe, in all its states, before outcome(s)  (depending on how you see that/those later state(s)).

that can actually be thought of as a 'mind state' too, although then purely subjectively (non scientifically) described, the one in where you 'stop thinking', very popular in Zen meditation. It's not the same really, but to me it seem to have similarities. yor_on, Fri, 10th Oct 2014

I was thinking of the Turing test there actually.  the one where you can't decide if it is a machine or a human you talk too. If we know 'sci fi' :) would get to talk to a 'rock' of some sort, using this test to decide. would that make the rock more 'evolutionary intelligent' than the example in where we would code a computer artificially. It's a side track though. yor_on, Fri, 10th Oct 2014

The point using emergences may be that you're correct in one way, as is Penrose. This consciousness, intelligence, etc is more than the sum of its parts. And it is just that that fascinates me :)

On the other tentacle, what an emergence seem to state is that it is a logical process from underlying causes, meaning that it can come from 'anywhere', if the right pre-combination existing. that's what i mean by wondering if it has to be carbon based. yor_on, Fri, 10th Oct 2014

If I understand correctly the emergencies could be understood (at least the weak one). For example we can deterministically explain/trace-back the wet-ability of water from only 2 water molecules. If the emergent property is the result of the collective motion of thousands/millions of molecules, that collective motion can be identified and therefore the emergence understood and no explanatory gap left.

In the case of consciousness the question is: how a circuit element (in brain) generate (say) redness and aware perception of redness? There still seems to be an explanatory gap between the flow of ions/e- on a certain path (in brain) and the aware perception of redness arising with/from that ion/e- flow. 

flr, Fri, 10th Oct 2014

Not really. "In philosophy, systems theory, science, and art, emergence is conceived as a process whereby larger entities, patterns, and regularities arise through interactions among smaller or simpler entities that themselves do not exhibit such properties." Sure, we know the constituents, but what they present us with emerging is new information. yor_on, Fri, 10th Oct 2014

Depending upon the level of intelligence our friendly computer had, that statement could well be argued with. Ethos_, Fri, 10th Oct 2014

Most of the things you feel, touch, smell and taste should be results of emergences. Like sugar being a logical shape of molecules, fitting receptors in your mouth, your brain emerging with a taste of 'sweetness'. Just as you dip your hand in a glass of water, to find a wetness.

Sweetness and sugar is actually a very good description of a emergence, as an artificial sweetener only have to have a better geometric fit to my mouths receptors to make me find my coffee disgustingly 'sweet', all as I understands it. yor_on, Fri, 10th Oct 2014

Then it is possible to conceive the emergent properties from simpler elements that do not have it. The emergent property does not came as a mystery, instead it could be conceived. It does not came as a mystery out of nowhere, there has to be some logic connections with the parts that could be traced out.

Also, I would argue that in the case of weak emergencies conceived=deterministically understood.

You skipped a step, the most important one. After tasting a candy the signal from receptors is transited to the brain. Then the neurons in brain will fire up in a certain pattern. The feel of sweetness is strongly correlated with this particular pattern of electric flow through axons in the brain (indeed, if this neuronal pattern is disrupted I may not feel any sweetness).
Why a feel of sweetness appears from a certain electrical pattern? How an electric pattern generate a subjective experience of sweetness? How could we conceive the feel of sweetness from an electric pattern?

flr, Fri, 10th Oct 2014

You could ask the same from the geometric shape it need to have. Because that is pure geometry as I get it, not chemistry as such. Defining it that way, 'thoughts' definitely belong there too. yor_on, Fri, 10th Oct 2014

What you seem to wonder about is whether you could define some  emergence to a specific electrochemical stimulation of the brain though? And that I think should be possible, but I'm not sure? If we use the geometry as a pointer then it is the geometry, shouldn't matter what molecules that geometry consist of, to make the brain emerge with 'sweet!!!'. And it is also so that I think, although not a hundred percent sure, that this 'sweet' experience is more than a cultural, social experience, It's what I think 'hardwired' into the brain. yor_on, Fri, 10th Oct 2014

How and why a certain neuronal firing pattern generate the feel of sweetness?
How and why an electrochemical circuit in brain generates 1st person subjective feeling? Why not that neuronal firing pattern 'go dark' and no-one experiences nothing?

I guess I am just skeptic that the Identity Theory is sufficient. flr, Fri, 10th Oct 2014

I have begun to wonder whether the Turing test is just a tautology.

Turing began with a need to define intelligent behaviour, and settled on "behaviour indistinguishable from a human being". Like it or not, this depends on two factors: the ability of the machine to behave, and the ability of a person to distinguish between two responses.

Consider a simple mechanical test. Switch on a light in a dark room. We sort of expect humans and indeed all animals and plants to be attracted towards the light, and we would distinguish a vampire or a zombie by its turning away from the light. Both are intelligent responses, inasmuch as they are voluntary (OK, the plant case is debatable, but sunflowers rotate anticlockwise in the southern hemisphere) actions associated with the survival of the subject, but we have prejudged one of them as being nonhuman, so it would fail the Turing test. 

Now walk into a starlit field and ask "where's the rabbit?" A human would say "I have no idea" and a dog would find it by smell and sound and bring it back to you. Widely different responses, but which one is the more intelligent? Turing foresaw some of this problem by limiting his test to text input and output, but surely the underlying criterion of intelligence here is "the ability to surprise the questioner". 

So what Turing comes down to is "two things are indistinguishable if you can't distinguish between them". alancalverd, Sat, 11th Oct 2014

Consciousness and awareness may just be illusions. I recently read an interesting op ed by the author of the book Consciousness and the Social Brain on the New York Times (

This professor of psychology and cognition at Princeton believes that our "self awareness" is just a mental construct, and that we don't actually perceive as much as we think we do. An interesting read. chiralSPO, Sat, 11th Oct 2014

I am very sure that I have aware thought now as I am writing this post. Actually that is the most important quality that I posses: to became aware of the environment and of myself.
Another example: I am quite sure I was clearly aware of a hunger feeling before having my breakfast this morning.

Indeed, only objective aspects can be a study of science however that does not mean we should  deny the subjective aspect of consciousness. It is not even necessary....

The eliminitivists argue that other theories of consciousness are based on intuition and the intuition can be wrong therefore we shall not trust those theories.
However eliminitivists' theory is also based on their own intuition (see the double standard here?) .

Finally, if the consciousness does not exist or it is just an illusion then that paper (the link you pointed) was not the result of the aware thoughts of a sentient being. Then why should I even care about it?

A lazy way to 'solve' a problem is to pretend the problem does not exists in the first place.
flr, Sun, 12th Oct 2014

I am very sure that I have aware thought now as I am writing this post. Actually that is the most important quality that I posses: to became aware of the environment and of myself.
Another example: I am quite sure I was clearly aware of a hunger feeling before having my breakfast this morning.

Indeed, only objective aspects can be a study of science however that does not mean we should  deny the subjective aspect of consciousness. It is not even necessary....

The eliminitivists argue that other theories of consciousness are based on intuition and the intuition can be wrong therefore we shall not trust those theories.
However eliminitivists' theory is also based on their own intuition (see the double standard here?) .

Finally, if the consciousness does not exist or it is just an illusion then that paper (the link you pointed) was not the result of the aware thoughts of a sentient being. Then why should I even care about it?

A lazy way to 'solve' a problem is to pretend the problem does not exists in the first place.

I am not saying that it is certainly an illusion and doesn't require further study, but I do think that is a possibility that shouldn't be discounted off-hand. Our current understanding of consciousness may be akin to the 19th century's understanding of the Ether--something that must be there to allow light to propagate, but cannot be measured in any way--ultimately we learned that it was a problem with the model, and there was no Ether, not that it was impossible to observe/measure/study it.

I see three possibilities: consciousness is real and can be explained by (materialist) science; consciousness is real but cannot be measured in any way other than experiencing it; or consciousness is not actually real, or at least, is very different from what we think it is. At this point I don't think there is enough data to support any of these over the others. chiralSPO, Tue, 14th Oct 2014

I am very sure that I have aware thought now as I am writing this post. Actually that is the most important quality that I posses: to became aware of the environment and of myself.
Another example: I am quite sure I was clearly aware of a hunger feeling before having my breakfast this morning.

Also, one must consider the malleability of awareness, both of self and of the surroundings. A common effect of psychedelics such as mescaline, psilocybin, DMT or LSD in high doses is "depersonalization," in which someone either loses their concept of self, or dissociates it from their bodies (they may identify as an object, their surroundings or the universe). This could be taken as evidence that our minds are separate from our bodies, or it could be taken as evidence of the limitations of our perceptions. chiralSPO, Tue, 14th Oct 2014

But the 'receiver' of the aware experience is still the same even if the aware experience is perceived as somewhat modified. flr, Tue, 14th Oct 2014

Heard a guy pointing out that we only have a limited amount of different receptors when it comes to drugs. As I gathered it his point was that there are a lot of possible 'drugs' that have no effect at all on us as we lack the equipment to experience them. And what I think it knits to is your argument flr, that there always should be 'something' experiencing it. yor_on, Thu, 16th Oct 2014

I'll make a argument now :)

Ethics yor_on, Fri, 17th Oct 2014

We have departed from the original question, and settled on a debate about consciousness.

I think an important piece of this debate that has only tangentially been brought up, is which beings have consciousness and which do not?

Are only humans conscious? If so, at what point did the first human have its first conscious thought? Are humans conscious from conception on, or does it "turn on"? Can it turn off?

Are other animals conscious? If so, which? How can we tell? Perhaps plants are conscious... perhaps computers are conscious, we just can't know the answer to any of these questions if consciousness is only self detecting. How do I know you are conscious--do I take you at your word? chiralSPO, Mon, 20th Oct 2014

Tell us what the word means, and we'll come up with an answer. alancalverd, Mon, 20th Oct 2014

Tell us what the word means, and we'll come up with an answer.

I think the responsibility of defining consciousness lies squarely on those positing that there is such a thing. chiralSPO, Tue, 21st Oct 2014

I'd say that anything which can be asleep can also be conscious. PmbPhy, Tue, 21st Oct 2014

I have dormant trees in my garden right now. They are alive, but not growing or doing anything to actively modify their environment or defend themselves (e.g. producing and exuding weedkillers or insecticides). Are they asleep? alancalverd, Tue, 21st Oct 2014

my laptop computer sleeps almost every night  chiralSPO, Tue, 21st Oct 2014

Related to above questions, perhaps one may find interesting the conference posted on-line at the web-address:
See also their 'Declaration':

flr, Thu, 23rd Oct 2014

An unambiguous definition of consciousness is elusive, but if you take the ability to report awareness of some event as an indicator of human consciousness, you can examine the activity of the brain to see if there is some characteristic neural signature that correlates with this indicator.

Stanislaus Deheane (author of 'Consciousness and the Brain') has done extensive studies on subjects who were given various stimuli at increasing intensities, or masked in various ways, so that there came a threshold point at which they reported being aware of the stimulus. Comparing the brain activity signatures in response to the stimulus, he found that stimuli below conscious awareness would produce limited activity in localised areas of the brain. However, when the stimuli crossed the threshold of awareness, that localised activity developed into a characteristic wave of activation that swept across the brain activating many different areas and 'reverberating' for some time before dying away.

Subsequently, this characteristic activity signal has been used to identify levels of consciousness in patients in a persistent vegetative state - i.e. to distinguish between 'locked-in' syndrome and coma, with great success, even identifying patients that could be stimulated into conscious wakefulness.

Tests on animals have shown that in mammals trained to report awareness, when tested (including macaque monkeys and mice) show similar responses and a similar wide area activation pattern when stimuli reach a certain threshold, suggesting something similar to consciousness. Babies of two months old (I don't know if they've tested earlier ages) show the same wide activation in response to spoken language, and the language areas are involved; interestingly, the response is large, but very much slower than in adults, due to the lack of myelination of the neurons at that age - they effectively think in slow motion.

Plants don't have an integrated information processing system like the central nervous system, so there's no way they can be conscious in the sense that animals are conscious. But it would be interesting to see whether other animals, particularly non-mammals, that show some behavioural characteristics associated with consciousness (e.g. octopuses and some birds) show similar patterns of neural activity when actively responding to stimuli. dlorde, Thu, 23rd Oct 2014

Oooh, something measurable, I like it!

I would bet on octopuses as a likely candidate for having consciousness of some sort, given their obvious intelligence and apparent personality. I'm not sure how similar we could expect it to be to ours though, especially given the autonomy their arms have...

I think I most like the idea of consciousness as an emergent property of our complex neural systems, but as far as I know there is only speculation on what the requirements are to support this emergence. It would be interesting to be able to test and measure several animals for signs of similarity to our consciousness. chiralSPO, Thu, 23rd Oct 2014

It's a tricky question - we only have our own consciousness as a baseline; how different from ours must complex behaviours be before we don't recognise or acknowledge them as conscious? If we could establish octopus consciousness, it would necessarily be recognisably similar to ours, but could we ever know how similar?  Their nervous systems are so different - multiple ganglia rather than a single central processor, that our neural activity measures might not be applicable (though I'd bet on some common features).

If we do establish they have similarities of consciousness, it would surely say something profound about consciousness in general, as - being molluscs - they would have evolved it quite independently; which would suggest strongly convergent evolution of intelligence & consciousness even in alien environments and body configurations.
dlorde, Fri, 24th Oct 2014

I don't know, but I expect at least animals, as dogs, horses, cats etc to be conscious. Although to go from that to define them as intelligent is trickier, but so it is with defining a IQ for a human. If you want, animals have souls :)

eh, probably should have made that 'self conscious', knowing that they 'exist'. To go from that to a 'mirror test' in where you expect some animal to recognize itself is more of using 'intelligence' to me. But they have feelings, just as us, and they will feel pain. yor_on, Fri, 24th Oct 2014

And what is a soul?  :)

flr, Fri, 24th Oct 2014

heh :)

That was for those wanting it flr. I don't know what a soul is, but it seems to be important for a lot of people. Maybe it's what the Egyptians called 'kaa'? (if that now is the correct spelling of it?) yor_on, Fri, 24th Oct 2014

Webster's....soul: "an entity without material reality, regarded as the spiritual part of a person."

That is, of course, if one believes in the after life? Ethos_, Fri, 24th Oct 2014

At last, something measurable, definable, and probably useful! It illuminates the distinction between an autonomic and a conscious response in a powerfully mechanistic way.

My surmise is that the subconscious (autonomic) response is the hardwired firmware that keeps the body alive, and the conscious response derives from learning, i.e. forming soft associations between stimuli and responses. This also bears on intelligence, which to my mind is "the ability to surprise an observer" and comes from making associations which are not clearly directly relevant to the stimulus. 

Consider an oldfashioned "IQ" test involving a set of line drawings. The autonomic response is to fixate on a bunch of black lines on a white paper - a baby will do that. The soft association is to name the shapes, "triangle, circle, boat, fish...." and the intelligence test is to spot the connection between what they represent, and to identify the odd one out or predict the next in the series, i.e. to abstract a common property. This explains some of the objections to conventional intelligence tests (if you've never seen a boat or a fish, or they aren't represented that way in your culture, you can't make the unlearned connection because the learned bit is missing).

Many thanks, dlorde, for a powerful insight.

As for dogs and octopi, yes, they can recognise symbols (principally gestures and sounds, in the case of dogs, and defnitely geometric shapes in octopi) and they can "surprise the observer" by responding nonreflexively. Simple case: I whistle for my dog to come to me. If she is dozing or just randomly sniffing her environment, the learned response is fairly instantaneous, but if she is chasing a rabbit or eating, she makes a conscious decision to finish the job and then come to me.  The element of "surprise" is that I don't always know where she is or what she is doing when I whistle, so she is making a decision based on stuff that she knows and I don't.  alancalverd, Fri, 24th Oct 2014

Yes; although it seems to me that in IQ tests (and in general) consciously aware thinking (System 2) is concerned mainly with controlling the focus of attention and marshalling the resources of the powerful parallel processing of the subconscious (System 1) thinking - a bit like a teacher coordinating with a class of smart students, using the suggestions they shout out to solve a problem, using the whiteboard as working memory. The teacher keeps the long term goal in mind, getting the students to solve the problem by continually bouncing their suggestions back to them with new questions. The teacher does none of the low-level problem solving; even when choosing between suggestions to focus on, he'll bounce the decision back to the class - 'what looks like the most likely option?'.

This, to me, feels like a better fit with the short evolutionary history of high-level conscious activity. There hasn't been time to evolve much more than a coordinator (System 2) with a scratch-pad, to harness the one-shot abilities of System 1 thinking into chains of coherent, goal-oriented thought. dlorde, Sat, 25th Oct 2014

At last, something measurable, definable, and probably useful! It illuminates the distinction between an autonomic and a conscious response in a powerfully mechanistic way.

Actually it does not say anything about the most important aspect of consciousness: the 1st person subjective experience.
Why should a certain neuronal pathway (no matter how complicated and geometrical complex is) generate subjective experience for that particular individual?

For example, let's assume you have a very powerful experimental technique (NMR or whatever) which can tell exactly what happens in my brain when I eat (say) chocolate. In other words you can determine the neurons excitation pathway that is correlated with what I perceive as 'sweet'.  Well, in such a case you only got a 3rd person view of some neuronal pathway and not the 1st person feel of sweetness. What you will be missing will be the most essential aspect: how is it to feel sweet for me .

We became conscious when neurons are firing a more complex pattern and based on that there are objective criteria to asses if a person is aware based on the brain activity.
But why those neurons and more complex neuronal pathway generate a conscious feel and why "it seems" specifically directed for me only that it generate a sense of self for me only?
How a sense of "self" (and awareness) is generated from something insentient such as neurons and neuronal pathways (and electric circuits)?

flr, Wed, 29th Oct 2014

I suspect that the answer is likely to be because that neural pathway contributes to (is part of) your awareness, and that's how it feels when that pathway is active. Not very satisfying or explanatory, I know, but sometimes things just are what they are.

That's rather obvious - your brain is genetically and developmentally unique, and tailored by your unique lifetime experiences; only you can know how things feel for you because only you feel them, and in a way unique to you. Others can only map your symbolic interpretation onto their own experience.

Those neurons generate a conscious feel because for humans as a whole that's what turned out to give us a better chance of successfully reproducing (presumably for social reasons). IOW, the 'why' is evolution. I don't understand what you're asking in the second half of that sentence - why should your brain generate a sense of self for only you? who else could it generate a sense of self for, and why would it generate a sense of self for anyone else? Sense of self is intimately connected with your individual physical sensorium - your sensory perspective (seeing, touching, hearing, location, etc.); a sense of ownership (your body & mind belong to you); a sense of agency (that you control your body's actions); internal feelings (you can sense your body regardless of the external environment). These are all specific to you and they don't just exist by default, they are explicitly constructed as part of generating your sense of self.

Damage to the areas that generate these sensations or integrate them into the self that is 'you', can result in weird problems like Cotard's Syndrome (thinking you're dead), Alien Hand Syndrome (thinking your hand - or other body part - doesn't belong to you, or is being operated by someone else), or various forms of dissociation, where you lose your sense of location, or identity, or your sense of self expands to encompass everything around you (trippy!).

For reasonably current details of what we know about the generation and construction of self, I recommend Antonio Damasio's "Self Comes To Mind". As to how neurons firing together make feelings and sensations - as I said above, the mental you is the firings of those neurons, and I don't anticipate a better answer than that's how it is to be an active bunch of neurons connected up in that particular way. We can explain specific aspects of perception and experience in terms of information processing, but only personal experience can tell you what it's like to be the information processor involved. dlorde, Wed, 29th Oct 2014

That reflects the view of identity theory that mental states = neuronal states. In short, that just like lightening = electric discharge (or sound = pressure waves through fluids) , the identity theories state that mental states = neuronal states and nothing else.

However, for A=B , A and B must have the same properties, if B has a property that A does not posses then the equality is not true.
Then some objections to identity theory could be formulated as follows:
i) a) neuronal states are physical states and there is an ontologic reality of them.
    b) there appears be no ontological reality of mental states. For example the 'redness' of the 'red' is how my mind map the red for me. Red exists as ontologic entity but not 'redness'. 'Redness' appears to me as something 'virtual' in my mind only, but the neuronal state that generate 'redness' is real thing.
ii) a) neuronal states can be viewed by everyone. they can be objectively measurable.
    b) mental states are strictly private to the subject; i.e. only I know what is in front of me now, not you.
iii) b) mental states have 'about-ness' or intentionality. For example I love my wife. The subject of my mental state 'love' is a person.
    a) neuronal states have no intentionality whatsoever; how could possible a flux of ions/e- care abut my wife?
iv) b) Based on mental states that follows the rationale: "If A=B is true and B=C is true then always A=C is true" one can understand it as a valid judgment or a truth.
      a) But if you follow with that super-NMR-aparatus all corresponding neuronal states needed to judge the above statement , where in those neuronal states (which again, are no more that ions/e- flux) is the value of truth?


There may be a principal problem with the token identity theory:
Let's assume that in a billions years from now a super-advanced tech/civ. can duplicate exactly the brain of AAA, into a new copy BBB. I would expect that BBB has its own private mind as it is a brain separated from AAA. But the neuronal states on BBB which are identical to those in AAA brain (they are exact copies) do not generate mental states in AAA but instead in BBB. That would negate the token identity theory.


  It appears to me that mental states are caused by neuronal states but not identical to them. That means: there is still a missing piece needed to explain how mental arises from physical states.
flr, Thu, 30th Oct 2014

I found this interesting video: flr, Sun, 2nd Nov 2014

Has anyone ever read Schrodinger's book What is Life? It's online and can be downloaded at PmbPhy, Sun, 2nd Nov 2014

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