There are arguments confirming and denying that animals have consciousness. Some arguments say that not even all humans have consciousness, e.g. small babies.

Which observable signs do exist that indicate that another being (animal, baby, ...) may be conscious?

Following these signs, what would be the consequences of animals or some humans (not) being conscious?

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    There's a few inter-related terms that might need disentangling for this to be a great question: sentience, awareness, etc. Turing considered the problem so intractable that he argued replacing the trait "being conscious" with "can be mistaken for a human in conversation," at any rate with respect to hypothetical artificial intelligences. "Is conscious" is difficult to measure in any straightforward way at all; it's the sort of trait we replace experimentally with a proxy (for instance the Turing Test.)
    – Joseph Weissman
    Commented Jun 7, 2011 at 23:42
  • You mean being concious reltive to a human?, a being capable of doing tera flops calculations would also ask wether the human kettle also have a conciousness at some minuscle level.
    – jimjim
    Commented Jun 7, 2011 at 23:43
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    @Joe: Right, we need a definition of consciousness before considering this problem.
    – Cerberus
    Commented Jun 7, 2011 at 23:50
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    Joe has some good points, except that the Turing Test has proved to be a horrible way of determining whether something is conscious or not.
    – Jeff
    Commented Jun 7, 2011 at 23:51
  • Is this question about dualism or a science based on, e.g. neuro-science?
    – Chris S
    Commented Jun 9, 2011 at 18:00

6 Answers 6


If you mean consciousnesses as the existence of subjective experience ("Qualia"), then there's probably no way to distinguish between an entity with qualia, and an entity with out one. Even when we consider adult, healthy people, we can't know "if there's somebody in there".

The term p-zombie is used to describe (hypothetical) entities that don't have qualia, but appear just like regular people.

The only thing I can think of that such p-zombies can't do, is understand the concept of qualia. so in a society consisting of only p-zombies, I would expect this term wouldn't exist.

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    Doesn't your last paragraph imply a deviation from consciousness as an epiphenomenon (i.e. why Frank Jackson got confused about Mary)?
    – Ruben
    Commented Jun 8, 2011 at 8:51
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    I disagree with your last paragraph. For one, p-zombies don't understand anything, so it isn't unusual for them to not understand qualia. For another, they are, by definition, behaviorally identical to humans, as such, they would be able to have all the same discussions about qualia as we do.
    – dimo414
    Commented Jun 10, 2011 at 7:21
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    @dimo414 regarding you 2nd sentence. p-zombies are a thought experiment. the question is "can there be entities that appear just like humans, but lack qualia". my last sentence claims that the answer might be 'no', because those these p-zombies wouldn't come p with the concept of qualia by themselves (they might discuss it after hearing about it from entities with qualia) Commented Jun 10, 2011 at 19:27
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    The thought experiment pivots on the fact that the p-zombies behave identically to humans. If you can identify such a trivial and easy to detect distinction, then we're no longer talking about the thought experiment as it's proposed. While I'm willing to be told otherwise, I have always thought of p-zombies as thinking-less automata, which simply respond to stimuli exactly like us. To "lack conscious experience, qualia, or sentience" (Wikipedia) seems to me to imply they lack any sort of behavior parallel to what we would call consciously thinking.
    – dimo414
    Commented Jun 10, 2011 at 20:28
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    @dimo414 the idea behind p-zombies (at least the way I understand it) is that there is no " behavior parallel to what we would call consciously thinking." - that is, there could be p-zombies that behave just like humans, but lack qualia. if there are behaviors (or any objective measurements - including various method to probe the brain like MRI, EEG...) that depend on qualia, then the hypothesis about p-zombies would be falsified. Commented Jun 11, 2011 at 13:55

Only a partial list, but here are a few traits that lead people to believe X is conscious. Note that none of these are "necessary" traits, they're certainly not "sufficient", and all of these traits lie on a continuum (they can't be reduced to checkboxes). Also note that these are traits that lead people to believe X is conscious, not traits that make X conscious. While the two are surely correlated, this is an important distinction.

  • Learning: Does X show evidence of learning? If X is put in the same situation many times, does it do better on some criterion over time? Or does it make the mistakes? This criterion has been rolled in with adaptation to the environment.

  • Perception: Does X take its environment as input, in order to make decisions? It doesn't necessarily have to have eyes and hands, but does it react to its environment in a suitable way?

  • Intelligence: Is X able to solve 'hard' problems? Can it do math or play chess? I don't really like this criterion because it is quite subjective, yet it seems humans are willing to base their decision on subjective criteria like this. Imagine what a human living 2,000 years ago would think of today's computers-- would they be deemed conscious?

  • Planning: While humans and animals make plenty of spur-of-the-moment decisions, they also seem to make quite a lot of decisions that involve foresight. Does X show foresight, or does it just hill climb?

  • Creativity (insight): Can X abstract its own knowledge, such as making analogies? Can it apply solutions from one problem to another similar-looking problem? Can it form novel solutions based on abstract knowledge, or can it only solve novel problems by chance and repetition?

  • Similarity: We "know" that humans are conscious. The more similar something is to us, the more likely we are to judge it as conscious. We are quite adept at distinguishing biological movement from aritificial movement, and the same goes for language. This criterion is a bit different from the others on the list, because we often believe the other traits to defining features of consciousness, where this is merely an indicator.

What would be the consequences of some animals or humans not being conscious? Probably not much, but that's my opinion. The world goes on as it has, now with new labels. Our conceptions of ethics and what it means to be human would change, but the outside world remains the same.

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    I would add indicators of being self aware (as per @Hal's answer).
    – Dave
    Commented Jun 20, 2013 at 17:18

The fast answer is, "the being's ability to recognize itself in a mirror."

There are a handful of animals that can do this (Elephants, Dolphins, and some primates). The most common way to test whether an animal apprehends that its reflection is an image of itself, is to mark the animal and observe whether it attempts to remove the mark when it sees the mark on itself in the mirror.


First Justification


Consciousness has degree of sensitiveness with abilities to:

  • Aware of something

    • It's perceive differences
  • Feeling something

    • It's focusing on something

Degree of sensitiveness

Different degree of perceive differences can be measured by:

  1. Answering "how many dimensional can be perceived?" The more surfaces with different dimensional can be perceived by something, the more something can be considered having more consciousness (more aware)

  2. Answering "how many for the details of specific surface of specific dimensional can be perceived?" The more the details of specific surface of specific dimensional can be perceived by something, the more something can be considered having more consciousness (more aware)

Different degree of feeling (focusing on) something can be measured by:

  1. Answering "how many dimensional can be focused on?" The more surfaces with different dimensional can be focused on, the more something can be considered having more consciousness (specific feeling with more intense).

  2. Answering "how close for something can be focused on?" The closer for the surfaces with different dimensional can be focused on, the more something can be considered having more consciousness (specific feeling with more intense).

Any kind of justification to make sure whether a being has consciousness must be closer to these requirements.


  • Animals and plants having abilities to differentiate for the purposes to fulfill their needs.

  • Animals and plants having abilities to focus on specific directions for the purposes to fulfill their needs.

  • Therefore animals and plants are having consciousness, but with different degree of consciousness.

If we make a comparison to human. Human having abilities to do as animals and plants did but with wider ranges. It puts human as being with higher consciousness.

Compared to zombies, since zombies have abilities as already described, then zombie must be considered having new consciousness differently to previous consciousness (whether it might be considered from subconscious or being possessed).

Final (Advanced & Limited) Justification

  • Intelligent

    • It's an act of defense that can maintain the viability of an organism or living things (their selves). Similarly, a smart community can defend the community itself from collapsing. The more standard needs of a community or a living thing can be maintained, and the more often it happens, it is increasingly showing its intelligence.
  • Switching off consciousness

    • It's about decreasing consciousness become less aware and less focus.

    We could experience it when we were sleeping, meditating or being hypnotized.

If other beings can act intelligently also what they perceive and what they focus on something can be switched off and switched on again, this indicates strongly that those beings have consciousness.

  • Considering switching off consciousness may not be applied to plants (yet), but at least for human, animals or zombies may be proceed by applying general anaesthetic.

The points are:

  • There is degree of consciousness.

  • According to First Justification, human, animals & plants are conscious being with different degree of consciousness

  • Whether a device (body) is possessed by subconscious or conscious, it may be asserted as conscious being.

  • To be more specific, according to Final Justification, human, animals and any other beings that may be switched off for their consciousness using general anaesthetic, they can be considered as conscious being.


A slightly different definition from what other answerers use of "conscious" is "able to feel pain." Varner gives six suggestive criteria:

  1. Having nociceptors
  2. Having a centralized nervous system
  3. Having nociceptors connected to CNS
  4. Producing endogenous opiods
  5. Having a physiological response affected by pain-killers
  6. Having a behavioral response to painful stimuli

If you follow that link, you can see that there is strong evidence to believe that at least vertebrates feel pain. The consequences are (in Varner's opinion) a moral imperative for veganism.

  • What does consciousness have to do with the ability to feel pain? Why accept this biological definition of pain? Why not define pain more simply as a command to change the environment, and allow that plants and rocks also feel pain? Commented Jun 16, 2011 at 6:52
  • @Dan: Consciousness is often described as something like "an organism's awareness of itself." Certainly being able to say "I am in pain" implies being able to say "I", thus pain is a marker of consciousness. The reason why we would suspect plants and rocks are not conscious is too long to fit in a comment, so I must refer you to Varner's work. (Or any work on philosophy of mind, for that matter.)
    – Xodarap
    Commented Jun 16, 2011 at 15:55
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    I think this answer is too Earth-centric. Surely if we encountered a species that looked and behaved exactly like us, except that they didn't satisfy 1-4, we wouldn't hesitate to call them conscious. Perhaps this is a biological test of consciousness, but it can't be an exclusive philosophical one.
    – Jeff
    Commented Jun 16, 2011 at 18:25
  • @Jeff: I certainly agree - that is why I called them "suggestive." They do have the benefit of being easily testable, whereas e.g. defining "conscious" as "can learn" just shifts the question to how we define "learn". So I'm not convinced it's a bad answer.
    – Xodarap
    Commented Jun 16, 2011 at 18:32
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    No, it's not a bad answer, I was just presenting an instance in which these criteria do not hold up. I agree that defining "learning" can be ambiguous and subjective, and I agree that it's shifting the question-- but it's shifting the question from a non-observable (consciousness) to an observable (learning).
    – Jeff
    Commented Jun 16, 2011 at 19:10

Maybe we are making a mistake by saying that consciousness is something which fully exists or doesn't at all, like a on/off thing.

Maybe even a bacteria has some degree of consciousness, given they do feel things and they do have a sense of self. Maybe even an atomic particle does. Maybe consciousness is a property of the universe, maybe it's the view of things from the inside, while physical science is the view from the "outside".

Of course this is a problem if we want to respect all sentient beings! We already aren't because our immune system is killing thousands of bacteria right now :O

(I'm sorry but I can't still post in the comments)

  • In your answer could you cite an author making such an argument? (e.g. Chalmer's pan-psychism, Searle's comments on Animal Consciousness, etc.) And maybe elaborate on these arguments as they relate to the author's question? Either way, an interesting comment & welcome to philosophy.SE!
    – MmmHmm
    Commented Mar 13, 2017 at 17:07

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