Why do Aliens have such large heads?

[The Ultimate Predator]

I mean, obviously to look cool, but any other reasons. Its very heavy, and they need the tail for balance, so its a hindrance in ways...

[AtR]

Need to keep their large brains together, so as the inner jaw thing. But that's just my guess.

[Dark Predalien]

my theory is that the aliens (may) have any other organs in the head

[ian36015]

in AVP, when scar poped off the head it showed the large brain, if noticed you can see somthing moving inside. Brain pluse? Naa. when scar staps/ touchs it (dont remember) the inner jaws quickly strikes out and scare lex. So it seems its a brain and a chamber for the inner jaws

[ArchangeL]

It holds the brain and the mechanism for firing the inner jaws out.

Also, it looks cool.

[Mr. Weyland]

I think it might be for how they communicate, some form of telepathy, and to kept that big mouth thing in 

[Eidotemit]

Im sure there are several reasons for the aliens head being the way it is. We saw it chambers a large brain in AvP, it is a general assumption that the large brain is for some sort of esp communication (which there is evidence to support from the films, primarily A:R or AvP). The xenos have also demonstrated an ability to learn and process information quickly. The head is elongated probably to create better balance for the creature, especially when running on all fours.

[SiL]

Its very heavy, and they need the tail for balance,

Actually, that's what the tubes on the back are for, and why they're not there in Alien 3. Giger originally put them in to act as a counterbalance to the weight of the head - In Alien 3, as the creature mostly moved on all-fours the weight and balance would be over the shoulders, so the tubes were dropped.

At first the Alien had no tail, only the back spikes. The tail was a request of Scott's.

In reply to the topic, I stick to aesthetics rather than functionality

[Mr. Weyland]

Wasnt the tail on the front of the alien at one stage 

[SiL]

It was attached to the front during the scene with Brett, but it was always designed to be coming out the back.

[Mr. Weyland]

I though so, because if it was at the back of the Alien during that scene the tail might have snapped 

[Newsfop]

I believe the large head also is a receptor for sound and light information. It can fuction quite well in the dark, as we have all seen.

[Ava]

My theory is, that they have such a big heads cause they were designed by a male..but that´s just a guess

[Meathead320]

I bet they make jokes about humans behind our backs because our heads are small:

"HEY!! DID YOU SSSSEEE THE HUMAN'S HEAD, I JUST INNER JAW MASSSHED? IT WAS SOOO SMALLL, HHE HHHE HHHE"

[DB]

Well, gee, how else do you expect them to please something as big as the Queen's cavern? Everything else would be too small.

Queens gotta have fun, too.