[This is an ABC podcast - (Australian Broadcastong Corporation)]
G'day, Dr Karl here.
Now, doppelgänger is a German word, and it means somebody who looks just like you. But do we really each have, somewhere else on the planet, our own personal spitting image? Well, that mostly depends on how you define the word, "look-alike".
The idea that somebody exists who looks just like you goes back to the ancient Egyptians. But the actual word, "doppelgänger", was coined in a book written in 1796. The word "doppelgänger" literally means "double walker," or "double goer" in German.
The doppelgänger features in stories stretching back thousands of years. In Norse literature, your double arrives at your destination before you do, and simply gives the hosts warning that you are about to arrive.
But often, the doppelgänger has a malevolent or sinister import, for example a doppelgänger might imply threats, or, a warning of death.
In the Goode Olde Days, it was a little hard to find your double.
But when the World Wide Web and online photo sharing ramped up, finding people who looked remarkably alike, suddenly became very easy.
The Canadian artist, Francois Brunelle, has a project on the web called "I'm not a look-alike!". He posts photographs of people who are unrelated, but who indeed, look very similar. His project has been running for over two decades.
On first impressions, looking at the faces in his project one after the other, they do indeed look remarkably similar. But when you look closer at the faces side-by-side, you see differences in (for example) the curve of the upper or lower lip, the width of the upper or lower nose, the eyebrows, and so on.
When we humans look at another person to try to recognise them, overwhelmingly we first look at their eyes, then their mouth and then finally their nose – and nearly always in that specific order.
However, regardless of our eyes darting all over the face that we are trying to recognise, it appears that the encoding system used by our brain looks at the entire head — in a single snapshot. We know this from two famous photographs of two different US Presidents, and their matching Vice-Presidents.
One photo was called "Democrat Coalition" – showing Bill Clinton and Al Gore. The other was called "Republican Coalition" — and this time, the faces of George W Bush and Dick Cheney were placed side by side.
In each case, the individual Vice-President was very definitely recognisable, as themselves.
But in both photos, the eyes, nose and mouth of the Vice-President had been digitally replaced by the eyes, nose and mouth of their matching President.
So how could Al Gore still look like Al Gore – even though he had the eyes, nose and mouth of Bill Clinton? And Dick Cheney still look like Dick Cheney, even though his image had the eyes, nose and mouth of George W Bush?
What's going on?
It seems that "something" happens in your brain, in the process of recognising a face, that allows you to ignore the eyes, nose and mouth. We still do not understand this at all.
However, as a consolation prize, we do know that one brain area that helps identify faces is called the "fusiform gyrus".
Of course, these Democrat Coalition and Republican Coalition photoshopped images are not at all typical. After all, these four famous people were incredibly well known to many of us – and so, we already came with our internal expectation of what they actually looked like, and so, did accept them.
Today, facial recognition is used in passports, surveillance, security, your driver's license, unlocking your smart phone, and so on. But let's hope that the Artificial Intelligence software isn't as easy to fool as our brains seem to be.
So next time you think you've spotted your doppelgänger… it might be worth doing a double-take… and we'll double back on that next time.
G'day, Dr Karl here.
This time, I've got the second half of the doppelgänger story. But unlike your supposedly identical twin, this part of the story won't double up.
So how do you measure "identical"?
Well, This is what Dr Teghan Lucas, then at the University of Adelaide, tried to do.
Dr Lucas used standardised photographs of nearly 4,000 US military personnel - men and women aged 17 to 51. These photos were a small part of a US Army survey trying to measure people's dimensions.
Armed with the photos, Dr Lucas then trained a team of 22 people over some four weeks in how to make eight specific measurements of a human face.
These measurements included the distance all the way around the jaw from one ear to the other, the distance between the cheek bones, the distance between the pupils, the height of each ear, how far each ear protruded sideways, the left-right width of the skull, the front-back length of the skull, and the circumference of the skull.
As you would expect, the more measurements that she used, the more uniquely the team could identify an individual.
When the team used four of the eight measurements to identify the faces in the photographs, there were just 10 duplicates in her sample of 4,000 faces. But increasing the number of measurements to five reduced the number of people with the exact same measurements to zero.
Dr Lucas estimated that if she used all eight measurements, there would be a duplicate, or doppelgänger, only once every trillion faces. That's a lot of faces - roughly 100 times greater than the human population.
But remember, these nearly 4,000 photographs were taken with compliant military subjects under very rigorously controlled lighting situations, facial poses, orientation of the head and so on.
When a surveillance camera catches a facial image on the street or inside a hardware store, the situation is much less controlled - for example, someone could be chatting very animatedly, or staring coldly.
And this "real life setting" brings us to a recent Spanish study. They started off by selecting 32 lookalikes from the Canadian website "I'm not a lookalike".
Then they used three commercially available facial recognition programs. These programs were each quite different – the first was designed for classifying faces, the second for surveillance, while the third was optimised for general facial analysis.
Quite separately, each of these three programs had been trained with millions of facial images from many thousands of people, in quite a range of circumstances and lighting. And just to finish off, each of these programs used 20-or-more measurements of the human face to try to make a match – not just eight.
When the three facial recognition apps analysed the 32 pairs of look-alikes, they agreed that the people in each of some 16 pairs were identical –at least, "identical" for the programs. Thirteen pairs were European, with the remaining three being Hispanic, East Asian and South-Central Asian.
Curiously, slightly more than half (that is, nine) of the 16 pairs had very similar DNA - in the technical sense that they shared a lot of single nucleotide polymorphisms (or SNPs). But that left seven pairs (almost half) that did not have these genetic similarities.
Of course, 16 pairs is not a very large sample size, so we can't place too much reliability on this initial study. Personally, when I looked very carefully at each of the doppelgangers, I could see quite distinct differences in the curvature of the lips, the shape of the eyebrows, how far the mouth opened left-to-right in a smile and so on. So while it was difficult, it was not impossible to tell the couples apart.
However, in each of the 16 pairs of people, the really weird thing was as well as looking alike, the couples were remarkably similar in their heights, weights, lifestyles and behaviours - even down to their sports interests, their smoking habits and their levels of education. This result suggests that at least some of your inherent DNA, your "nature", can affect not just your appearance, but your life choices. Of course, we know that "nurture", or how you are brought up, also has a very significant effect.
Better future research could even help predict the likelihood of certain diseases, just by looking at a face.
So if the eyes are the windows to the soul, maybe the face is the window to your DNA?
Next time you see your doppelganger, strike up a chat - you may have more in common than just your looks!
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