Do you recognise the people in the picture above? They are, of course, Jane Goodall – British primatologist and anthropologist – and the actor, author and comedian Stephen Fry.

Recognising the identity of these people from their faces may have seemed effortless. But for some people, recognising the faces of famous people is very difficult. In fact, such people often fail to recognise the faces of their children, spouse, parents, close friends, work colleagues and sometimes even themselves in a mirror.

This inability to recognise faces is known as “face blindness” or prosopagnosia (from Greek: “prosopon” = “face”; “agnosia” = “not knowing”). Prosopagnosia is not the same as forgetting names (which happens to everyone!), rather it’s the problem of not being able to use someone’s face to determine their identity.

The following quote from David Fine, a prosopagnosic whose story appeared in the British Medical Journal in 2011, illustrates just how severe prosopagnosia can be and the effects the condition can have on mental health, relationships and occupational success:

“I often fail to recognise my children or even my wife … I have failed to acknowledge friends and, more distressingly, those in authority.

At school I would get lines for not raising my cap to a teacher … As a young man I ignored girls whom I had met the night before – not a good mating strategy.

I find networking all but impossible, and social situations, from parties to conferences, may cause acute anxiety… I know other staff members by their uniforms and badges. In party clothes, with different hairstyles, they are strangers to me.”

People with prosopagnosia know they are looking at a face but the face does not convey information about identity. As such, people find they use other cues, such as voice, gait or context, to identify people. To quote David Fine again:

“I memorise hair, jewellery, and favourite clothes. I recognise gaits, tics, and voices … Above all I rely on context: a person of a certain type in our corridor is my colleague — but in the supermarket is probably a stranger.”

People with prosopagnosia can usually see perfectly well, and as such they can often tell other similar objects apart, such as two cars. Many people with prosopagnosia are also able to extract other types of information from faces, such as the expression displayed and the direction of the person’s eye gaze.

In these cases, prosopagnosia is a selective impairment in extracting identifying information from a face.

Acquired prosopagnosia

Some cases of prosopagnosia are acquired, in which a person who was previously able to recognise faces has a traumatic brain injury – such as a stroke – which damages the parts of the brain used to recognise faces.

Many brain regions are involved in processing faces, however damage to regions involved in face and object processing in the occipital and temporal lobes (see image below) are most likely to result in prosopagnosia.

Congenital prosopagnosia

Cases of acquired prosopagnosia have been reported in the neurological literature since the mid-19th century. More recently, it has also become apparent that people can also have severe difficulty recognising faces without having a brain injury.

These people have what is known as congenital or developmental prosopagnosia and have failed to develop face identity recognition mechanisms. People with congenital prosopagnosia, such as David Fine, have been unable to recognise faces for as long as they can remember.

There are a number of high-profile individuals who have had lifelong face recognition difficulties. These include popular scientist Dr. Karl Kruszelnicki, portrait painter Chuck Close, neuroscientist Oliver Sacks and, as you may have guessed, the two people in the image at the top of this story: Stephen Fry and Jane Goodall.

In 2007, we established the Australian Prosopagnosia Register where people who suspect they have congenital prosopagnosia are able to register their interest to participate in research.

These people report severe, recurring, everyday face recognition difficulties, such as failing to recognise their child at day care or having difficulty following the plot of movies because they cannot differentiate the actors.

The prevalence of congenital prosopagnosia is estimated at between 2-2.9% of the adult educated population. Given this, it’s perhaps not surprising that hundreds of people have registered with our website, and thousands of people have registered on similar registers in the US and UK.

Thanks to the generosity of those who volunteer their time, we now know that congenital prosopagnosia sometimes runs in families, and therefore may have a genetic basis.

Research has also shown that people with prosopagnosia seem to have difficulty seeing the face as a whole and instead seem to focus on individual parts. Moreover, they may spend more time looking at parts of the face that aren’t that useful for distinguishing between faces – such as the hairline – rather than other regions which may be more diagnostic, such as the eyes.

Research is also beginning to reveal the neural basis of congenital prosopagnosia. And people are working on developing training programs that people with prosopagnosia can use to improve their face recognition.

So next time you see someone and instantly know who they are, consider yourself lucky: imagine if that never happened.