Skulls and eyeballs

Sorry for the crazy sounding title… I’m not getting ready for halloween, I just couldn’t really think what else to call it! I was just wondering a couple of things and thought this might be the place to ask…

First, are all human eyes the same size? I know that vision problems can be caused by the eyeball being too long or short, but I mean from the front - In two people, will their eyes be the same size when you’re looking at their face? I would have guessed that they would since it seems like the optics of an eye would need to be constant, but it looks like some people have bigger or smaller eye… Is this just an illusion?

Second question is similar, but about the skull… Now I know that people’s skulls are different sizes and shapes (Hat sizes!), but what exactly is going on there? I would assume that brains are the same size for everyone, and probably the inside of the skull too, so do people with bigger heads just have thicker skulls?

I hope someone can enlighten me, thanks for any answers!

Welcome to SDMB Cakey.

You seem to be making some assumptions that may be misleading you. When you look at someone’s face the apparent size of their eyes has little to do with the diameter of the eyebal but the eyelid opening. This varies a lot as with some people the normal opening doesn’t even full expose the iris, the colored part of the eye, while in others it is full exposed with white visible all around.

Why should everyone’s brain be the same size? Why should eyeballs be the same size? Eyes don’t need to be a specific size to work, they need to have all their own dimenions be proportionate to each other.

Thank you for the welcome!

Sorry, my first question wasn’t really clear - I was actually meaning the size of the eyeball itself when viewed from the front, not the actual visible parts of the eye… sorry about that!

So eyes and brains can vary in size? That’s very interesting! The eyes make sense, it hadn’t occured to me that it would just be their proportions that are important, I had just been thinking that the whole visual apparatus would need to be pretty precise to focus images clearly…

I’m surprised that brains vary though! I would have thought that, with all the different areas of the brain having their specific functions and all of it being used, a change in size would be quite significant… Does it actually have any effect?

Do you happen to have any idea of what sort of size of variation is possible? Even a rough scale… a difference of millimetres, centimetres?

Thanks very much for your help anyway!

There is a rare birth defect where people are born with mostly spinal fluid where their brain should be. The surprising thing is usually the condition goes undetected. These people lead normal, functioning lives, until one day they die and have an autopsy, or for some reason they have a cat scan or an x-ray of their head done. Then whoever is doing the autopsy or scan goes “ha ha, ok guys, very funny, where did you put his brain?”

These folks tend to max out at about 130 on the IQ scale, which is surprisingly high considering that if you look at their skull it’s mostly fluid.

If a brain can survive that much of a development defect, I would think some minor variations in size wouldn’t mean squat.

FYI - Neanderthals had bigger brains that we do, but all indications are they were less intelligent. They made tools, art, and jewelry the same way we do, but if you look at examples of the time, their stuff was simpler than the stuff made by our ancestors. Size matters to some degree (you just aren’t going to see an intelligent mouse), but mostly it’s how the neurons are all interconnected that makes the big difference. I have read that there is a slight correlation between brain size and IQ, but brain size alone is not a good predictor of IQ.

It’s worth pointing out that elephants have rather gigantic brains, but are not as smart as us. They’re afraid of mice, after all. On the other hand, I hear they have superb retention skills.

Brains aren’t manufactured at the end state like a microprocessor, they are grown and each one is different since the “programming,” the connections between neurons isn’t separate from the structure.

Ah yes, now that you mention it I remember hearing that… I did know that brain size wasn’t necessarily linked to intelligence, but I was thinking that within a species it would have some sort of effect, maybe not on actual intelligence but on some function of the brain… it’s really amazing just how adaptable those squishy grey lumps are!

Thank you all for your replies, I just have one more question, though maybe I should write a little background (Long and boring, skip if you want!)

The reason I was actually interested in this in the first place was that I was thinking about doing a little project… I’m thinking about taking pictures of celebrities who’re considered attractive and tracing over their prominent facial features (Nose, chin, etc) in a photo-editor, then removing the actual photo so you’re left with a line image.

That sounds… really quite strange when I say it like that, but it’s really just come from some idle curiosity - I realised that several of the celebrities I find attractive have pretty prominent brows (Tom Cruise and David Boreanez for example), and I wondered if there were other trends like that - They’d be a lot easier to spot in a simplified line image than a photo.

The main problem is that since I’d have to rely on pictures from the web and things, they’d all be of different sizes and to compare the line images they’d really need to be the same size.

Which brings me in a meandering way to my point - I needed some sort of constant between human faces to use as a reference. I thought that the iris of the eyes would work quite well, but now I’m wondering if it might not…
So, do you think the eyeball varies enough that it would throw things off? And more to the point, can you think of any other constant between human faces that might work better?

Phew, if you read through all that then I salute and thank you, and if you have any thoughts I’d be even more grateful still! :smiley:

As for proportions, the eyes are about halfway up the skull, but I’m sure that varies quite a bit, even if you have some way of allowing for hair so you can find the top. The best I can think of is to measure lots of things and see what ratios seem to predict attractiveness. (Try eye spacing, width of cheekbones, width of mouth, length of nose, and so on.)

I’ll also note that lots of photo editors have built-in edge finders. Look for ‘Filters’ or ‘Plug-ins’ on the menu somewhere. Some work best in only one direction, so you might have to rotate the pic 90 degrees to find some edges.

Let us know how it goes!

Cakey … have you ever seen the TLC special The Human Face, hosted by John Cleese? Or the associated book (also called The Human Face)?

Methinks you would have great interest in both.

The thing with rendering people’s faces into minimal line drawings to help make certain features more pronounced … that’s not in the least weird. I have seen that kind of thing done on television (I believe it was on one of Desmond Morris’ The Human Animal episodes). Stripping away some of the details of the face is a good way to make comparisons that focus on a small set of features.

Hm, I don’t think I’ve seen that Bordelond, I’ll definitely keep my eyes open! It looks like amazon only has a limited stock but maybe I’ll get a used copy from there or ebay. Thanks for the recommendation!

RJK, actually, someone’s already done the ratio thing! Apparently the perfect proportion is 1.618:1, known as the ‘Golden Ratio’ or Phi… there’s quite a bit of information about it here:

I’m not really sure why though but the ratio and even the mask they made up from it just don’t quite seem to ‘fit’ intuitively for me. Most likely they’re 100% correct, but I’d still quite like to do it myself to sort of be able to actually see ‘Oh yes, this nose is wider than this nose’ and things, and probably at the end I’ll try measuring and find out that everything was 1.618:1 all along… Still, it should be interesting at least :wink:

I’ll be giving it a try when I get some free time… thanks very much to you all for your help!