Natural 'bar codes' help us recognise faces, study shows
4 April 2009
The study, published today in the open access 'Journal of Vision', may have implications for improving face recognition software.
Faces are unique in their ability to convey a vast range of information about people, including their gender, age and mood. For social animals such as humans, the ability to locate a face is important, as this is where we pick up many of our cues for social interactions.
While recognising a person's face is clearly a complex process, the first steps to processing visual information in the brain are thought to be more basic and rely on the orientation of features such as lines.
By manipulating images of the faces of celebrities such as Coldplay's Chris Martin and actor George Clooney, Dr Steven Dakin at University College London (UCL) Institute of Ophthalmology and Professor Roger Watt from the University of Stirling showed that nearly all of the information that we need to recognise faces is contained in horizontal lines, such as the line of the eyebrows, the eyes and the lips. Further analysis revealed that these features could be simplified into black and white lines of information - in other words, bar codes.
"Exposed skin on our forehead and cheeks tends to be shiny whilst our eyebrows and lips and the shadows cast in the eye sockets and under the nose tend to be darker," says Dr Dakin. "The resulting horizontal stripes of information are reminiscent of a supermarket bar code."
Bar codes were developed as an efficient way of providing information: straight, one-dimensional lines are far easier to process than two-dimensional characters such as numbers. In a similar way, our faces may have evolved to allow us to effectively convey the information needed to recognise them.
The researchers analysed various natural images, such as flowers and landscapes, and found that faces are unique in conveying all their useful information in horizontal stripes. The bar code pattern has many advantages: it can be recognised efficiently by the visual parts of the brain, is easy to locate in complex scenes and appears to be resistant to changes in the overall appearance of the face.
This latter point - our ability to recognise a distorted face - is illustrated through images of Marlon Brando, whose face has very striking features and is easily represented as a bar code. When his face is squashed or stretched, viewed from an angle or cast in shadows, Brando is still easily recognisable - and the bar code representation remains relatively unchanged. Viewing a negative of the photograph or seeing his face upside-down, however, makes it more difficult to recognise - likewise, the equivalent bar code appears very different.
Distorted images of Marlon Brando. Credit: Journal of Vision
Dr Dakin believes the research may have implications for improving face recognition software, for example in busy public spaces where police may need to locate a suspect in a crowd on CCTV cameras. The ability of such software to recognise individuals has improved vastly, but is still poor at the first step - locating faces in complex scenes.
"To improve face recognition software, we need to look towards biology and see how we have solved the problem," he says. "If we are looking for bar-code-like images to tell us that 'this is a face', then software could be developed to mimic this skill."
The research may also help to explain our ability to see faces where they do not exist, for example in clouds or in flames.
"Our faces are fairly symmetrical, and it is this symmetry that creates horizontal patterns," explains Dr Dakin. "Local symmetry can occur in natural phenomena, such as fire, and it could be that our brains recognise a barcode when a face isn't really there."
Image: Enhanced image showing facial information carried in horizontal 'bar codes'.
Credit: iStockphoto/Jacob Wackerhausen/Steven Dakin
Contact
Craig Brierley
Senior Media Officer
Wellcome Trust
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Notes for editors
1. Dakin SC, Watt RJ. Biological “bar codes” in human faces. Journal of Vision 2009 3 April.
2. The Wellcome Trust is the largest charity in the UK. It funds innovative biomedical research, in the UK and internationally, spending over £600 million each year to support the brightest scientists with the best ideas. The Wellcome Trust supports public debate about biomedical research and its impact on health and wellbeing.
3. UCL (University College London) - founded in 1826, UCL was the first English university established after Oxford and Cambridge, the first to admit students regardless of race, class, religion or gender, and the first to provide systematic teaching of law, architecture and medicine. UCL is the seventh-ranked university in the 2008 THES-QS World University Rankings, and the third-ranked UK university in the 2008 league table of the top 500 world universities produced by the Shanghai Jiao Tong University. UCL alumni include Marie Stopes, Jonathan Dimbleby, Lord Woolf, Alexander Graham Bell and members of the band Coldplay. UCL currently has over 12 000 undergraduate and 8000 postgraduate students. Its annual income is over £600 million.
4. The University of Stirling, founded by Royal Charter in 1967, was the first genuinely new University in Scotland for over 400 years. Stirling has 8200 undergraduates and 3200 postgraduates, with around 2000 staff.It has a strong cosmopolitan feel, with over 80 nationalities represented on campus, and 19 per cent of students coming from outside the UK. The University is located just two miles from the centre of Stirling, which received city status in 2002. Set in the shadow of the Ochil Hills, the magnificent 310-acre campus encompasses a loch, a golf course and the 18th-century Airthrey Castle. It is undoubtedly one of the most attractive campuses in Europe, and the University also has campuses in Inverness and Stornoway. Famous alumni include the novelist Iain Banks, and former Home Secretary Dr John Reid.