I've been referred to here from https://philosophy.stackexchange.com/questions/8052/why-are-things-conscious. Could you guys help out? Here's the question:

What is the reason for animals or more general entities being conscious? How did this evolve? What is the advantage?

I'm aware of ideas that consciousness is merely a illusion, however I find them less than convincing. The counter-argument would follow the line "if consciousness is an illusion, who has the illusion and more importantly why?". Additionally I believe that consciousness is a bare empirical fact. Even more, it is the basis for empirical thought. That "consciousness is an illusion" is not a good idea has been discussed by e.g. Searle (a video can be found here http://www.youtube.com/watch?v=yCii726A4Jc)

So what are good explanatory models for consciousness?

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    $\begingroup$ What is the operational definition of consciousness you are using? I believe it is a very vague and often ill-defined term that generally leads to unproductive discussions. $\endgroup$
    – Memming
    Sep 2, 2013 at 22:39
  • $\begingroup$ Look up Gazzaniga's left brain interpretor idea on google. $\endgroup$
    – area51
    Sep 2, 2013 at 23:58
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    $\begingroup$ There are two very different questions here i) Why are things conscious and ii) What are some good models for consciousness. Could you narrow this down? $\endgroup$
    – terdon
    Sep 3, 2013 at 3:38
  • $\begingroup$ Actually, my first urge was to say, things are not conscious, otherwise I would not call them a "thing" anymore. But I guess that's more a question for the SE site this actually came from. $\endgroup$
    – skymningen
    Sep 3, 2013 at 6:25
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    $\begingroup$ Well, that's the thing, "consciousness" is a very vague and human-centric term. How can we know if other animals posses it? How do you define it? Where do you draw the line? $\endgroup$
    – terdon
    Sep 3, 2013 at 13:16

3 Answers 3


Disclaimer: there is a very large amount of literature on the subject and I am in no way expert enough to properly review it here.

In any case, here's a few papers that review the issue and may serve as a basis to look up other references

Evolution of consciousness: phylogeny, ontogeny, and emergence from general anesthesia - Mashour and Alkire, PNAS 2013

We propose that the stepwise emergence from general anesthesia can serve as a reproducible model to study the evolution of consciousness across various species and use current data from anesthesiology to shed light on the phylogeny of consciousness. Ultimately, we conclude that the neurobiological structure of the vertebrate central nervous system is evolutionarily ancient and highly conserved across species and that the basic neurophysiologic mechanisms supporting consciousness in humans are found at the earliest points of vertebrate brain evolution.
[...] The distinction between phenomenal and access consciousness was noted, but phenomenal consciousness itself reflects the dissociable neurobiologica processes of awareness and arousal. Awareness refers to the content of consciousness (red apple vs. blue sky), whereas arousal refers to brain activation and level-of-consciousness (alert vs. drowsy vs. asleep vs. anesthetized). A number of current theories about consciousness propose that the cortex is the primary site containing the neural correlates of awareness, whereas midline subcortical brain structures provide ascending arousal influences to the cortex

This is also reviewed in this paper:

Subjective experience is probably not limited to humans: the evidence from neurobiology and behavior. - Baars, Conscious Cogn., 2005

Thus consciousness is not a metaphysical absolute, but a scientific construct like any other. In humans, the standard behavioral index of conscious cognition is accurate or verifiable report. It has been used scientifically since the beginning of psychophysics in the 1820s. Accurate report is highly reliable, but of course it is subject to limitations like any other empirical measure (Baars, 1988).
In humans the thalamus and cortex are crucial for supporting the contents of consciousness (Edelman & Tononi, 2000). Thalamus is often considered to be an extension of cortex, an added sandwich of interacting layers that controls most traffic to and from cortex. Local damage to cortical sensory regions, like the fusiform gyrus for face perception, results in a loss of conscious knowledge about faces but not about other visual features like color, location, or size. If the intralaminar nuclei of the thalamus are lesioned bilaterally, the conscious state is lost. By comparison, large lesions to cerebellum, basal ganglia, and spinal cord do not impair either conscious contents or state. Cerebellar damage can cause paralysis but not loss of consciousness. Lesion evidence on these points is supported by stimulation experiments using electrodes, transcranial magnetic stimulation (TMS), and microdialysis. It is also reflected in functional brain imaging. The evidence is therefore very strong that the T-C system supports consciousness. That is why many neuroscientists consider the T-C system to be the “seat” of conscious experience, and have done so for at least a century.

Again, citing from the first paper:

The recent experiments with general anesthesia in humans suggest that phylogenetically ancient structures in the brainstem and diencephalon—with only limited neocortical involvement—are sufficient to support primitive consciousness. Where, then, does consciousness arise on the evolutionary timeline? One might be tempted to conclude that consciousness commenced as our mammalian ancestors evolved just beyond reptiles and their predominantly subcortical brains. However, paleontological findings suggest that the synapsid line that gave rise to mammals and the sauropsid line that gave rise to reptiles and birds both diverged from the primitive anapsid line at a single point ~315 million years ago. Furthermore, there is significant evidence that avian species are capable of higher cognition and even consciousness itself. For example, birds demonstrate evidence of explicit episodic recall (i.e., conscious memory of an event) and theory of mind (i.e., attribution of subjective mental events to another being). Thus, it would be misguided to try to identify a single point at which consciousness emerged because evidence suggests that consciousness evolved along two independent lineages.


While it's still a very philosophical question, and neuroscience is not my speciality, I think that selfconscious comes from the integration of several informational sources.

Our brain has maps, that's a fact. We have maps to locate sensorial signals (in fact, all our senses are neural maps representations), to locate our muscles and we even have secondary maps that allow to compare the movements we desire to make and the movements we are actually making. The integration of all of this maps leads to a pretty accurate idea of ourself, and that's critical for selfconciousness.

Furthermore, our brains uses our senses to create images of our immediate sorroundings. They also need to locate other important places (for instance, even if you're at home you would proably have a mental idea of how far your workplace is). Moreover, we have a psicological idea of time wich places ourselfes in a present after a bunch of events that have already happened andd before a set of possible events that we have modelized or predicted with the information from the past. All of this creates an idea of our place in the world.

By combining this two ideas we have a global mental model of our own state, our own desires, our own characteristics, etc... placed in an mental image of the world based in our previous experience. Of course memories and thoughts would have its place, too, but they are more complicated to explain briefly.

Transversely, I don't think that computers would develop selfconciousness by its own even if someday they have more computational power than the brain. First, a computer doesn't need an idea of itself as a phisical being, unless it is programmed to do so (a robot would probably have it, thought). Second, the inner logical architecture of computers and brains is quite different, being maybe the lack of biologycal instincts the most relevant difference. Of course all of this should be programmable. My point is that is quite unlikely that it appears by itself and that a selfconcious computer is a pretty unpractical device.

  • $\begingroup$ +1 @Miguel (although I'm not signed up here) for actually posting an answer and a good one too. Besides this, I'm still wondering how neural maps are able to lead to the experiences we have. I simply can't see the mechanism there. That is besides stating that this is what neural maps do. To me this is "spooky action at a distance", i.e. not a real explanation. And I won't believe that a PC will have actual consciousness rather than simulated one until I see very solid proof for it. But an honest thanks still for the answer. There are really good points in there. $\endgroup$
    – pandita
    Sep 3, 2013 at 13:10

Neuroscience is my specialty. What we call consciousness is thought to be an evolutionary elaboration of a property of cells called "irritability", which is the cell's ability to respond to signals from its environment. There are many manifestations of this: chemicals binding to protein receptors, light interacting with proteins (as in photosynthesis), mechanical forces causing cell movement, bacterial chemo-taxis, and the list goes on.

The analogy is like this. What we call eating and elimination are analogous to cell metabolism. As a whole organism we must eat to replenish the body, and eliminate the waste produced. A single cell must also absorb nutrients to maintain itself and eliminate the waste products.

So, it is like a fractal. The same functions displayed by individual cells also manifest at the level of the whole organism. So, as the GI tract is the organ analogous to cell metabolism, the nervous system is the organ analogous to cell irritability. One could imagine that what we experience as our personal consciousness is in fact like taking an integral over the irritability of all the cells in our nervous system. Many people focus on the neurons, but all the cells in the brain contribute to the brain's function.

Now, this form of explanation is not really an explanation as much as it is a description of our biology. The obvious question arises: why are cells irritable? Because, irritability is basically the individual consciousness of an individual cell. Well, one then realizes that the response properties of cells to stimuli come from the action of the molecules and forces that make up the cell. The immediate forces are non-covalent interactions, mainly poorly understood even in terms of physics, such as forms of adhesion (consider Velcro or glue). These are emergent properties that stem from the assemblage of molecules of which cells are composed.

But let us grant that physicists eventually come to understand such "derived" forces in terms of the elementary four forces of the universe: electromagnetism, gravity, strong and weak nuclear. Then, it is clear that there is a potential contained in these forces to combine in ways that cause complex molecular assemblies that self-organize and display irritability.

Thus, the issue of consciousness presumably links back to somehow being an inherent emergent property of the forces of nature.

Again, this is all relatively uncontroversial, but building such a chain of explanation is not really an explanation as much as just being a description of how things are organized in the world. And I think it is clear to any thinking person that a description of something is not the same as an explanation of something.

So, if you follow this far, then you can appreciate why the Greeks thought that Atlas, who held up the world, stood on the back of a tortoise, and this tortoise was on top of another tortoise who was on top of another tortoise, all the way to infinity.

We have simply replaced Atlas and the tortoises with language of modern science. It is still an infinite regress. The short answer to "why are things conscious" is that it seems to be a property of the universe to display consciousness.

Now, there is one great man who thought about this problem and constructed what I consider the best explanation. This was Gottfried Leibniz, the man who invented calculus. Leibniz invented the idea of a "monad", and he considered monads as the basic units, the atoms, in the sense of being the indivisible units of reality. The monad, as an atom, is pure consciousness. So, Leibniz came to the conclusion that the reason there is consciousness is because consciousness is the fundamental building block of reality.

Monads are what everything is made of: us, cells, atoms, quarks, electrons, etc. These are all different forms of monads. According to Leibniz, they are all different forms of consciousness, and they combine in fractal patterns to make forms of consciousness within forms of consciousness within forms of consciousness. And this pattern goes in both directions from the infinitely small to the infinitely large. According to this idea, just because something does not seem to be conscious in the same form we are conscious does not mean it is not conscious.

This is how Leibniz solved what is called the "mind body problem", which is really the heading under which your question falls.

If one wishes merely for intellectual understanding of the nature of our consciousness, it is my opinion that Leibniz' ideas are the best available.

If you wish to go beyond mere intellectual understand to a deeper level of awareness of these issues, then I suggest you look up and study the works of a writer named Patanjali.

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    $\begingroup$ Could you please link to some literature at this regard? I never heard about "cell irritability" in the context of the nervous system, or when speaking of multicellular species for that matters. I think that for the scope of this site a proper neuroscience answer would have to be preferred to a phylosophical answer (Leibniz is all nice and good, but he was not what I would call a neuroscientist). $\endgroup$
    – nico
    Oct 20, 2013 at 9:27

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