Why are aliens (in science fiction books and film) so frequently depicted with two eyes?

It can all be traced back to that shite Roswell “autopsy”, the cliched oversized hairless head & black lifeless eyes image accelerated from that point on.
Same with the crackpots who believe they were abducted by aliens, always the same look…funny that.

Alien flies and spiders have multiple eyes, but aliens don’t have more than 2.

I dunno. I’ve read a lot of sci-fi and, in general, aliens are written to serve a purpose and what they look like is related to that. I could probably point out dozens of instances where aliens are written to not look like a human in any way.

Aliens on TV and film, though, is mostly due to budget constraints and what’s easy to do. It’s a lot easier to make humonoid aliens on TV but with the advent of decent CGI that could change quite a bit in the future.

In flims it is easier because the human actors who are dressing up as aliens have two eyes.

Because they have to be roughly human-shaped for actors to play them in the movies. Darn it, @JLeslie, you beat me to it! :)

One of my favourite STNG episodes, The Chase actually tries to give an explanation for why so many of the species we meet travelling through space are humanoid. I love that they made the attempt to address this bias with a plotline.

well when you think about it evolution wise it makes sense, for predator or prey animals, to have two eyes. One would not provide enough information, and more than two would be difficult, even for more advanced brains, to process. If you consider the forms of life on earth that have more than two eyes, they are generally fairly simple creatures, more of a stimulus and response animal, rather than thinking/planning.

Of course, alien life could evolve completely differently than this but it is likely that this would prove true, I think anyways.

I’m pretty sure there was Star Trek episode that explained this but I can’t remember if it was in TOS or TNG. Basically it boiled down to a common ancestor or something.

@glacial Let’s call it a tie. Jinx.

I don’t think we do or even can have the vaguest idea of what beings from other galaxy’s look like so we tend to stick with variations of what our puny imaginations can conjure.

If it’s hackneyed, pulp sci-fi types of movies, then @JLeslie‘s answer is most likely spot on. It’s easier to design a costume where the eyes actually are what the actor underneath sees through.

Thinking about creatures we know of, flies compound eyes are pretty weird looking. Their eyes are terrific at detecting motion, but pretty lousy at giving the fly a clear picture of what surrounds it and lays motionless. And even as odd as the fly eye appears, they do have two of them. There are a few outliers like the single eyed squid, and box jellies, which have 24 eyes around their bodies. Various sets the box jelly’s eyes are able to detect only certain wavelengths of radiation. One set of four is free to rotate in socket, always points up, and lets the jellyfish see the sky for navigation purposes. But in concert, the 24 eyes give the brainless stinging bastard of a squishy a pretty good picture of what’s around them.

But think about evolution on Earth, the exception proves the rule. Almost all creatures with any kind of advanced eye have 2 of them, set on opposite sides of their head. Grazing creatures (AKA prey) tend to have eyes on opposing sides of their skulls giving them a near 360 degree field of vision and thus helping them spot the motion of predators approaching no matter what angle they sneak in from. Predators, on the other hand, have two eyes in the front of their skulls, on opposite sides of their nose, giving them sharp binocular vision to see prey and calculate the distance to it. Good science fiction writers know this much science. They assume that life intelligent enough to travel through interstellar space would have gone through a predatory phase in its development. Having a really big brain requires more calories than grazing alone can easily provide.

I would add that sci-fi aliens are often used as metaphor. The genre offers a range of creative and oblique ways of exploring our own psyches. So sci-fi aliens are often less about extra-terrestrial life than about us. When used that way, they can’t be so unlike us that we’re unable to make a connection.

In film and TV, a lot of it has to do with the limitations of the available special effects. Back in the 60s when aliens were mostly played by an actor in a rubber mask, a basically-humanoid form was the only thing possible, and in franchises like Star Trek, the trope sticks. But with the advancement of special effects technology, film-makers have more room for creativity, so we can have more aliens like this

@thorninmud That’s what I’m thinking too. Ironically enough, for us to recognize an alien, it needs something we can relate to. Otherwise, it would no longer be an alien, but a monster instead, and there seems to be a vast difference between the two as far as sifi goes.

as an addendum to my last post I’m actually looking for a video showing the Shadows, which I think illustrate the point better than the Vorlons… can’t find one that shows them clearly though

@thorninmud I’m sure that plays a role. Even this ugly alien has enough features in common with us that we can project our basest predatory instincts into him and thus see ourselves.

Eyes evolved several times on Earth, and in each case the result was a pair of eyes. Maybe there is an advantage in having two eyes. Having two eyes provides predators with depth perception and prey with greater peripheral vision.

@ETpro Yeah. In one of the movies, a predator forges a bond with a human female. Granted, the bond comes from necessity, but it’s a bond nonetheless. We see that their culture, while it exists merely for the sole purpose of fighting, is similar to ours. That, based on the fact that while both human and predator can’t directly communicate with one another, they have no problem understanding enough to work together.

Gotta love em space Vikings. :D

Aliens are usually distorted reflections of ourselves, they aren’t really alien at all. Something entirely alien would be incomprehensible and unrecognisable.

@LostInParadise That’s pretty much what I said up here.

@Symbeline Go Vikings. They actually weren’t such bad guys unless you were their prey.

Because the two eyes system was “invented” numerous times independently here on Earth. It might be a universal evolutionary product.

@mattbrowne – huh? what do you mean by ‘invented’? Do you mean earth-based evolution? Or do you mean ‘invented’ by fiction writers?

@elbanditoroso – I meant “invented” by trial and error based on mutations and natural selection. Light sensitivity makes a lot of sense on exoplanets circling stars emitting light. It might be different on the dark world of rogue planets.

It might be because insects and flys ect. have many eyes or just 2 and the movie producer might have wanted it to look partly real.

Its because human beings like to anthropomorphize everything elbandito. =)

Personally, I like a little variety in my science fiction. Sure, I love the sexy women in tight, form fitting silver jumpsuits on the cover, but if there is a sentient crystal entity or a bipedal feline or a ten foot tall Gecko standing next to her, I don’t complain.

By the way, you also have to take into account that when you change the anatomy of the eye, not just the number and location of them, you change the wavelengths they can detect.

Bees for instance can see in the ultraviolet range, and that is how they identify flowers…