RadioLab has an interesting discussion between neurologist Oliver Sacks and artist Chuck Close about their experience of having prosopagnosia – the inability to recognise people by their faces.
The condition is often called ‘face blindness’ but the discussion gives a great illustration of why the label is so inaccurate because Chuck Close is famous for his detailed and evocative portraits of people’s faces.
At this point, it’s worth saying that there are various forms of prosopagnosia, an acquired version which people get after brain damage, and an inherited form, which Oliver Sacks and Chuck Close have.
You can see Close’s portraits online but you really need to see them in real life to experience their impact because they are typically huge (2-3 metres high) and incredibly detailed.
This shows that prosopagnosia is clearly not ‘face blindness’ – people with the condition can see faces fine – what they can’t do is distinguish people by their facial features. Faces just seem all the same – in the same way that you or I might have trouble distinguishing sheep by their faces.
We know a significant part of the difficulty is making sense of the structure of faces rather than their details. Statistically, human faces are very similar, and we have developed a way of perceiving faces that includes their overall layout.
You can demonstrate this process in action by simply by turning faces upside-down and showing that our ability to pick out differences is suddenly markedly reduced.
The Thatcher effect is probably the most striking example of this where changes to the eye and mouth seem hideous when the face is the right way up but when inverted we struggle to notice them.
This is because upright faces engage our perception of face structure into which the details are integrated. With upside-down faces we’re left having to do piecemeal feature-by-feature comparisons like a newspaper ‘spot the difference’ competition.
Music is a good analogy. If you heard sequences of disordered musical notes, some of which were identical and some of which had just one note different, you’d probably struggle to say which sequences were the same or different than the ones before.
But if you heard songs, some of which were identical and some of which had a single bum note, you’d easily pick out which were different because our understanding of the structure of melody makes discordant sounds stick out like a sore thumb.
Normal face perception is just picking up on the melody of faces while people with prosopagnosia generally lack this ability (although to different degrees).
In the RadioLab interview, Chuck Close says he paints faces by taking a photo, dividing it up into squares and then painting the canvas detail by detail.
In other words, he’s probably doing something similar to how he perceives faces. In fact, we might guess that Close’s prosopagnosia has given him a focus on detail which facilitates his striking portraits.
By the way, Chuck Close is a generally amazing guy and in 1988 suffered a stroke which left him partially paralysed and without the ability to coordinate his hands to paint such fine detail. Instead, he’s turned to painting portraits which are almost impressionist.
For each section of detail he paints the general pattern of light. Up close the paintings look incredibly abstract but when you step back they merge to form, amazingly, incredibly life-like face portraits.
Link to RadioLab on prosopagnosia.