How would we know that we have encountered extraterrestrial intelligence (ETI)? What would distinguish ETI from unintelligent aliens (like the parasite in Alien) and intelligent terrestrials (us)?
It may seem obvious that we can come up with an answer. We know of some intelligent things – ourselves. And we know about extraterrestrial things – planets, stars, interstellar clouds of vinegar.[1] One kind of ETI could be a combination of the two together: things like us, but from space. Consider the tall waving alien at the end of Close Encounters of the Third Kind.
But it is not enough to give an easy example. We cannot assume that the first ETIs we meet will be just like us. And how they might not be like us could make it hard for us to identify them at all.
1 Does It Matter that We Recognise Extraterrestrial Intelligence?
There are a number of reasons to care about whether or not something extraterrestrial we encounter is intelligent or not.
We Ought to Care More About Intelligent Things Than Non-Intelligent Things
Say we encounter something extraterrestrial which has something we want. For example, we come across something on a distant planet with a mineral for fuel. If it is not living, e.g., an asteroid, there seems to be no moral obstacle to simply taking it. Even if it is alive, there is no immediately obvious obstacle. If it is just some kind of extraterrestrial bacteria like the many types of bacteria on earth, there is no ethical question about using it. We take something essential to another living thing every time we eat, no matter how conscientious we find ourselves to be.
However, if ET is in any way intelligent, any way sentient, there are ethical issues. If something has the capacity for self-awareness, it looks safe to assume that it can suffer and there is some moral obligation toward it.
We might not care about that. Even if it suffers or is self-conscious, we may decide to take from it anyhow. We are human after all, and humans have a long history of colonialism and exploitation. If we are ethical, there is a problem with repeating that. But if we don’t care – if we are vicious not virtuous beings, are cruel or numb – then there is no problem.
However, that there is no problem assumes a situation in which we are the ones who are in the position to take from the ETI. We are in the position to conquer, colonise, exploit, or use it. Yet, for ETI, the more likely situation is that the ETI is in the dominant position. It can take something from us. If intelligence only evolved in this Solar System on Earth, it’s more likely that we’ll encounter ETI which is visiting us. If it visits us, it is more adaptable and empowered than we are. It can survive in space, an environment in which we barely exist. If it visits us, it can also enter our atmosphere. It can survive on Earth. Because it can live in space and on Earth, it is more adaptable, more flexible and robust. It is the one that is more capable of taking, of sailing down to us, loading up, and escaping any response from us.
We Can Interact Differently With Intelligent Things Than With Non-Intelligent Things
A second reason to care about recognizing ETI when we meet them is they open up a different set of possible interactions than opened by non-intelligent ETs. You can’t reason with unintelligent things. An asteroid rushing toward the Earth is not slowed down by your sound arguments. Just the same, alien bacteria that chemically synthesizes flesh is unmoved by suffering. However, if you can make yourself understood, an intelligent alien could be stopped doing what it is doing – you could ask it to slow its travel to Earth or to eat something other than your arm.
At least, you can ask it to do that if it recognises you.
2 Recognising Alien Intelligence
One oversight in many (though by no means all) science fiction stories is that intelligent beings that evolve in wildly different environments initially recognise each other as intelligent. Our heroes detect something approaching them and recognise them almost instantly as being sophisticated entities, with consciousness, self-awareness, and even ethical or rational capacities. Yet, when we encounter aliens the first time, there is no guarantee at all that it will look like an intelligent alien. There are several challenges to identifying it as such, including identifying what is not intelligent as intelligent. Furthermore, there is no guarantee that it will recognise us as intelligent beings.
In his short story ‘The Things’, Peter Watts narrates Carpenter’s ‘The Thing’ from the perspective of the alien.[2] It is a compassionate, intelligent being which does not understand humans at all. It is horrified by us. It sees us as empty and blind, lacking sentience, self or feeling.
When we encounter ETIs, it is possible we will not know – and neither will they. When it comes to sharing or taking, whoever has the better position may ignore the other’s cries to stop. This is not because they don’t care about what impact their actions have on other sentient beings; it is because they don’t know there are any such beings there.
So, how could we convince an ETI we are intelligent or sentient? And how could they convince us?
Language
It might be there is one feature that is unique to intelligent beings, even ETIs. Intelligent beings use language. If we encounter an extraterrestrial that uses language, then we know that the extraterrestrial is intelligent.
Here are three ways we might encounter an ETI language:
(a) There is communication aimed at us by something that understands us.
(b) There is communication aimed at us by something that does not understand us.
(c) There is communication not aimed at us at all (and which we only coincidentally encounter).
(a) is relatively easy to identify, as easy as a broadcast in a familiar human language. (b) is a common target of SETI and relatively simple as well. Intended for us, it should include patterns strongly indicative of intelligence, patterns which do not naturally occur but which all intelligent beings should know, e.g., sequences of primes. These sequences make sense if ETIs tries to communicate with us.
However, it’s reasonable to think that many – maybe most – ETI signals we pick up, whether we are aware of it or not, are (c). They are messages ETIs are sending amongst themselves. Human-directed broadcasts by humans, such as TV broadcasts or twitter spats, far outweigh ETI-directed ones, such as the Voyager probes. This is something we should also assume is true of ETI. In the first ETI we hear, we are more likely to be overhearing a discussion than have speech directed at us.
Whether or not we recognise it. Given an influential theory of language development, we may not be able to tell eavesdropped ETI conversations from noise.
According to Chomsky’s theory of language acquisition, the linguistic data available to an infant, such as her parents’ speech, is not enough for the infant to learn language. Yet, nearly every infant learns the language which surrounds them. Chomsky posits what Kukla[3] calls the Innateness Hypothesis: An infant is born with something, an innate module, to supplement the environmental data. This module is something that evolved in us; we are born with it, and it is uniquely attuned to the kinds of languages we, as humans, learn. Furthermore, as infants can typically learn any language, this module uses a ‘universal grammar’: typically, all children share a single protean grammar that allows them to learn any language they are exposed to.
Kukla argues that the innateness hypothesis raises a problem with communicating with ETI. Chomsky’s universal grammar applies only to human languages. It is not evidence that any language at all shares the grammar. The grammar may be ‘universal’ for humans. However, whatever structure it has evolves in humans. Any thing lacking the innate module can’t learn it the way one who possesses it can. And if the module is necessary to learn a language its attuned to, then those without it cannot learn that language. If our innate language modules evolved, then we and ETI are unlikely to share the same innate modules. We do not share the same evolutionary history.
One way out of this is convergent evolution. Perhaps the same module and grammar evolves under similar environments. Perhaps those environments exist in other places than Earth. If so, then we may encounter ETI which we can understand and which can understand us. Just as sharks and dolphins resemble each other, or kiwis and rodents, so humans and ETIs resemble each other. However, this is not guaranteed. Where environments are significantly different, creatures don’t so clearly converge in their features. The comparisons are a stretch. (Is the sea cucumber the kiwi of the sea?)
This omits all the other possible environments in which ETI may have evolved. If those other environments are more numerous than the environments like our own, then we are more likely to encounter an ETI from them. We are more likely to pick up their signals. If Chomsky is right, we are unlikely to understand most of the ETIs we encounter.
Technology
Perhaps we can avoid using language to detect ETI. If ETI does non-linguistic things that indicate intelligence, then we can still say “that’s intelligent” without it having to speak.
Here is one non-linguistic possibility: ETI exhibits awareness of mathematical, chemical, biological and physical principles. They are more technologically advanced than us. They turn up in gigantic starships hanging effortlessly in the sky. Their hulls are constructed of complex difficult-to-comprehend chemical alloys. When one of them is injured, they heal using advanced medical procedures.
Such traits may convince us that the extraterrestrial before us is intelligent. Advanced technology seems inconceivable without engineering plans, invention, devised and tested theories of physics, chemistry, an understanding of the body.
Yet, only recently did we grasp how bees fly: their flight was once thought impossible.[4] As the philosopher Dupré notes, not humans but microbes are “the most versatile and effective chemists in the biosphere” (Dupré, p.37[5]). And next time you cut yourself, look at the scar. Your body is repairing itself in a way no current doctor can.
All of these processes occur due to natural evolution — by definition, an unintelligent blind process. They are far more advanced than anything we can do now.
The complex giant ship hanging over your city may be the extraterrestrial equivalent of lichen. Its building of what seem like gigantic ships may be a megascopic lifeform’s growth or reshaping of its immune system.
Scale
There is one significant difference between lichen and that ship. Size. Lichen doesn’t grow that big or spread across space. This brings up one of the cheapest moves in most science fiction. We encounter aliens. They are pretty much the same size as us. 
One of the main reasons Earth life does not grow so huge relative to humans is because of gravity and heat. The different sizes and shapes regulate body temperature, allow movement, and allow creatures to eat. Elephants do not look like mice. Humans have soft tissue on the outside. Without it, when we move we would easily break. Insects, which are smaller, have no need of that tissue. A real Godzilla could not walk or even breath; he couldn’t even cool down.[6]
Yet, ET does not need to be so restricted. It did not evolve here on Earth. If an ET evolved, say, in the depths of an interstellar cloud, it is not clear what size or shape it could be. The morphology and scale of extraterrestrial life, including intelligent life, could vary as widely as extraterrestrial environments allow. (Anyone watching Rick & Morty will find this no surprise.)
The only reason to deny this possibility for intelligent aliens is if intelligence can only survive for any significant time in Earth-like environments. But if intelligence can only survive in Earth-like environments, then no ETI has crossed space to arrive here. Nor can we ourselves ever make it to meet them on their own world, or anywhere in-between.
There is a final way that size and shape might indicate intelligence. If ETI turns out to be the same scale as us, then, given the wide range of options, this would be so much a coincidence that it may be better to think it is intentional. The ET is copying us. It’s difficult to understand how this could be possible through natural selection. They didn’t evolve with us to mimic us. They would have to do it on arrival. The better explanation is they have studied us. These human-sized things may be like costumes worn to raise whooping cranes or fake animals to film animals.[7]
ETI are like us, despite coming from space. This shows they are intelligent. They are able to imitate us, talk like us, convince us they are not anything but another one of us. That would be excellent evidence that these aliens are as smart as we are. Because they are able to be just like we are.
However, if they could do that, then we couldn’t tell them apart from us. Instead of the ‘I’ in ‘ETI’ being difficult to work out, the ‘ET’ becomes difficult to work out. We may finally recognise an ETI as intelligent because it has tried so hard to be like us. But, if it doesn’t recognise us as intelligent, then it is unclear how they would ever take this approach.
A much earlier and less detailed version of this is published many years ago in Hackcircus #4, 2014.
[1] http://content.time.com/time/nation/article/0,8599,6778,00.html
[2] http://clarkesworldmagazine.com/watts_01_10/
[3] http://www.barnesandnoble.com/w/extraterrestrials-andrz-kukla/1101349873?ean=9780739142448
[4] http://www.caltech.edu/content/deciphering-mystery-bee-flight
[5] http://books.google.ie/books/about/The_Constituents_of_Life.html?id=eUqVEiDkzmcC&redir_esc=y
[6] http://www.cambridge.org/us/academic/subjects/life-sciences/zoology/scaling-why-animal-size-so-important
Sean Enda Power 