It's becoming obvious from how could humans recognize another species as sentient / intelligent that recognizing another species' intelligence is very complicated. There are no universal tests, no common definition of intelligence...

Let's go with one assumption: wherever we go in space, we'll be looking for extra-terrestrial life, and if we do find it (and recognize it as alive), we'll always try to learn if it is sentient.

Now what traits does a species need, to be recognized as intelligent by humans, beyond the fact that it is sentient and recognizable as alive by humans?

Differently put, this question could also be: what type of sentient species will we miss out because of our inability to recognize their sentience?

  • $\begingroup$ Not trying to upset you but this still seems to be the same thing. en.wikipedia.org/wiki/Intelligence $\endgroup$ – feas Apr 16 '15 at 20:52
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    $\begingroup$ @feas Here I'm asking what kind of sentient species we could recognize as such. In the other one I'm asking how we could recognize all kinds of sentient species as such. $\endgroup$ – Sheraff Apr 16 '15 at 20:54
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    $\begingroup$ What I'm trying to say is that this present question might be more answerable then. $\endgroup$ – Sheraff Apr 16 '15 at 20:56

While bees communicating the location of a food source through movement to others can be seen has intelligence, I don't believe humans as a whole would consider it significant enough. The minimum requirement could quite possibly be the ability to record history. It would not need to be as advanced as written text but the simple pictures in a cave showing migration to a food source for future generations.

  • $\begingroup$ By this logic, non-literate societies are composed of non-intelligent beings, unless "record history" is defined reciprocally to the question, i.e., tautologically, or so broadly as to include bees and ants (history as architecture, etc.). $\endgroup$ – CAgrippa Apr 17 '15 at 1:25
  • $\begingroup$ @CAgrippa interested in seeing your answer. Tautologically? Really? $\endgroup$ – feas Apr 17 '15 at 1:44
  • $\begingroup$ I think "oral history" should suffice, but again I'm left thinking, "Dolphins?" $\endgroup$ – Draco18s no longer trusts SE Feb 1 '16 at 20:29

To be successfully recognised as intelligent you first have to be recognised as life. Being recognised as life requires that metabolic rate and scale are tangible. If an organism meets every other criteria for intelligence but does it on a geological scale then everything that a human can observe in human terms will be ascribed to geological process.

Similarly, no matter how complicated our own activities, that organism would regard us as an unintelligent parasite.

So, to be recognised as intelligent by, and to some extent for that intelligence to be in any way relevant to, humans you have to act with a tempo within the grasp of humans.

Also, having a face helps.

  • $\begingroup$ I could have sworn I asked a question about "how would humans recognize an alien being as alive" (alien in the sense of far from our usual concepts). This is a cool answer in any case. $\endgroup$ – Sheraff Feb 2 '16 at 10:30
  • $\begingroup$ @Sheraff, Hm, so "don't be alien" isn't a great answer, then. Perhaps I shouldn't have gone so far as geological scale for an example. I think that if an intelligent super-organism comprised a forest (which we would acknowledge as alive), for example, we'd still be oblivious to it. Maybe I could scale it down further; but the problem is that there's no boundary between fanciful analogy and formal definition. Only that if it's not on our scale we simply don't care if it could be intelligent. $\endgroup$ – sh1 Feb 2 '16 at 17:32
  • $\begingroup$ Sorry I think I wasn't clear. I had understood your answer and I like it (as well as your clarification). But it prompted me to wonder "how could humans recognize something as alive", and I thought it was something I had asked (in another question) on this site. Which I probably didn't because answers to that would probably be along the lines of "we don't have a definition of what life is." $\endgroup$ – Sheraff Feb 2 '16 at 17:39

Intelligence is inherently linked to work. Work is an organized form of changing our environment. Bees and ants do work and change the environment, but they do so in a pattern organized by their genomes. Intelligent work is characterized by its capability to be taught to others of the same species. A human being is not born knowing how to build houses like ants do. It is taught how to do so by someone who already knows. This kind of accumulated knowledge that is first transmitted by alive members of the species, later evolves, with writing, as a multigeneration accumulation of knowledge and culture.

So, to verify if some species is intelligent you might ask:

  1. Does this species change the environment?
  2. Does this species change the environment via organized work?
  3. Does this species create new kinds of work and tools out of necessity?
  4. If this species does create new kinds of work and tools, does it do so by genetic change or learned behaviour?
  5. Does this species pass their knowledge from one generation to the next via teaching?
  6. Does this species write down their knowledge so it can be furthered by the next generations?

Up to the fourth question you are still in the realm of primate intelligence on Earth, because each one of those things can be done by various primate species. The questions five and six are humankind development.

  • $\begingroup$ I am not sure I agree. What if the species does not have the necessity of or the interest in changing its environment? What if the species has the ability to transmit knowledge without writing or communication (a little like if we could transmit our knowledge through DNA when procreating)? $\endgroup$ – Sheraff Apr 18 '15 at 17:00
  • $\begingroup$ the problem is that intelligence does not evolve as a full fledged intelligence out of nowhere, in other words you are applying current thinking to another era. Intelligence evolves in a species that is fully commited to the survival of the fittest, this intelligence will show itself in the fight for survival. First human to make a tool was not able to think "hey i might dont want to do anything with my intelligence". $\endgroup$ – Jorge Aldo Apr 18 '15 at 17:47
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    $\begingroup$ Actually, even the fifth question will still include some animals, including primates. Take a look at en.wikipedia.org/wiki/Cultural_transmission_in_animals. $\endgroup$ – Obie 2.0 Jul 22 '15 at 16:29
  • $\begingroup$ And the sixth excludes "primitive" human peoples and would have excluded most of the population of Europe a thousand years ago. $\endgroup$ – nigel222 Feb 1 '16 at 14:48
  • $\begingroup$ Somewhere in the list you need the mirror test. Assuming that the species had eyes, can individuals recognise that a mirror shows them their own body and eyes? Elephants and chimps can. Most animals can't. $\endgroup$ – nigel222 Feb 1 '16 at 14:56

Now what traits does a species need, to be recognized as intelligent by humans, beyond the fact that it is sentient and recognizable as alive by humans?

Differently put, this question could also be: what type of sentient species will >we miss out because of our inability to recognize their sentience?

The beings must:

1) Have the ability to accomplish complex tasks with results that are detectable (by humans), that are beyond the complexity achieved by non-sentient animals (as defined by the culture that encounters them), or

2) Have the (apparent) ability to communicate non-immediate or complex abstract concepts with one another (or with us), and

3) Operate on something close to the same timescale.

Or, to answer the reverse: Humans are not likely to recognize as sentient any race of beings that neither performs tasks more complex than nest-building or poking anthills with sticks, nor has any apparent means of communication more complex than required to signal dangers, the presence of food, the desire to mate, etc. Nor are we likely to recognize a sentience that requires day to say hello.


Motion will almost certainly be the most obvious thing that will make humans sit up and take notice. The ability to move, and to sense motion, is the subject of too many studies to mention. Conversely, if a species is sessile (and the spell checker sure doesn't like that word!), it will likely be overlooked for years, if it's ever spotted at all. Note that this isn't a requirement for sentience, just a focal point for human investigation.

Communication is probably the next biggest thing. Vocal communication attracts our attention as a species, and we tend to make big assumptions about species that don't operate this way. Electromagnetic phenomena will also almost certainly be noticed immediately. Body language is something that a trained observer would probably notice, especially if the species is highly gregarious, but this is the point at which arguments will develop about whether or not this form of communication constitutes sentient intelligence. Species that use chemical, "psychic" (for a certain value of psychic), and other more exotic forms of communication will almost certainly be overlooked for a long time.

Gregarity will also be a valuble clue. If a species, especially a spacefaring species, has such a sparse population as to rarely encounter other members of the same species, it might be hard to recognize an extraterrestrial species for what it is, never mind identify it as intelligent.

Technology is, of course, a dead giveaway, or it ought to be. Certainly anyone that thinks the great apes are sentient would see even the most primitive tech as a sign of intelligence. The famous termite fishing sticks come to mind.

Nervous Biology (Let the jokes begin!) For a species that isn't noted as sentient by any other method, biological examination might be used to try to determine the level of intelligence of that species. Current day scientists put a lot of stock in the Anthropic Principle, at least in the sense that they expect intelligent life to have a nervous system that functions like our does. Even xenobiologists that expect a physical nervous system radically different from our own aren't sure that they'll know what they're looking at when they see it. By this measure, if we ever accepted that some species with such a radically different biology was indeed sentient, we'd have much better clues to search for. Until then, only species that really resemble us are likely to be spotted in this way.

  • $\begingroup$ This is a great answer. I feel it still lacks the part mentioned by @sh1: "Being recognised as life requires that metabolic rate and scale are tangible." $\endgroup$ – Sheraff Sep 18 '16 at 21:05

They would need to have a visible way of communicating with each other. (if it are plants who communicate by thought it would take us a long time to find out probably).

They will also need to have some sort of language available, I know that there is a free PDF of NASA for xeno linguistics or something like that, here is a link:


They should also have a visible form of society, on a large scale. So no monkey congress/ tribes but more in the way of villages/ caravans/ nomads.

  • $\begingroup$ I agree that it would be like you say if we weren't actively looking for sentience in new species, but it is not the case. $\endgroup$ – Sheraff Apr 17 '15 at 12:24
  • $\begingroup$ Yeah by all means I am no specialist, but the link is a nice PDF though. It is also hard to tell what level of intellect OP wants to find. Must they be able to build stuff or is tribal enough. We are already looking for active space faring races. $\endgroup$ – Robin Apr 17 '15 at 12:27
  • $\begingroup$ I'm asking for sentient species and I am well aware of the problems that arise with this term... :-) $\endgroup$ – Sheraff Apr 17 '15 at 12:40

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