For one week in February 2015 all of us on the internet were avidly talking about a picture of a dress. Was the dress blue and black or gold and white? At first I was utterly convinced it was blue and black. Then a few years later I looked again and could clearly see it was gold and white. This image challenged an idea many of us take as given: that we all see the world in the same way.
We don’t – and this conclusion has been taken further in a new project called the Perception Census. Anil Seth, professor of neuroscience at Sussex University, and Fiona Macpherson, professor of philosophy at Glasgow University, are leading one of the largest research projects into human perception. They are inviting people to take part in a series of tasks to find out how we see and hear the world.
Of course, at one level, it is obvious we don’t all perceive the world in the same way. Many of us are either short-sighted or long-sighted, and need the aid of glasses or contact lenses to see the world clearly. Some of us are colourblind. We might well need hearing aids as we get older. And some people are born blind or deaf.
There are also the many optical and auditory illusions we have been familiar with for years: abstract images that look like faces or vases depending on which angle you look at them. And there are the high-frequency sounds that children can hear but older people can’t.
But it still feels somewhat odd to see an image of something fundamentally differently to someone else, when something as basic as colour is not shared between you. It raises a fundamental question: if my perception of what is blue is different to someone else’s, what is the real colour? Who is wrong or right? If we can’t even agree on the colour of something, what can we agree on as humans?
Anil Seth argues that we need to think in terms of “perceptual diversity” rather than trying to affirm the real colour or sound of something. As he writes in a piece for the Guardian, “the brain is continually making predictions about the causes of the sensory information it receives, and it uses that information to update its predictions.” Our minds are not simply windows that passively accept sensory data. We use the sensory data we receive to make patterns, trying to fit things together like a puzzle.
Context is everything. As part of the Perception Census, we are invited to complete tasks in which we are evaluated on how we perceive colour, sound or time. It quickly becomes apparent how big a role is played by our surrounding context and our imagination.
For example, there’s the Ebbinghaus illusion, named after Hermann Ebbinghaus, a German psychologist. In this task we see two circles surrounded by a group of other circles. The two circles are exactly the same size, but one of them appears bigger than the other. The bigger-looking circle is surrounded by a group of small circles. The smaller-looking circle is surrounded by a group of larger circles. This example vividly illustrates that we don’t notice things as they actually are; we see them in relation to their context. As Seth writes, “we live in a ‘controlled hallucination’ that remains tied to reality by a dance of prediction and correction, but which is never identical to that reality.”
Working through these tasks is illuminating – it shows me my particular way of seeing the world. I realise, for example, that I’m better at recognising faces than the average person, by doing well in the Craig Mooney face test, in which I see three black-and-white images and have to guess which one contains the eyes of a face.
But I also discover that I am bad at hearing musical pitches, through my struggle with a task in which I hear musical notes side by side that supposedly go higher and lower. In another auditory task I listen to a person repeating a short sentence in a speaking voice. The more I listen to that speaking voice, however, the more it sounds like it is singing.
There is much talk today of the need for political diversity, accepting that we don’t all see the world in the same ideological terms. Some of us put greater emphasis on the state to solve economic problems, while others believe this should be down to the market. In truth many of our beliefs are dependent on context. We might believe there is a time and a place for such-and-such a solution – tax cuts and deregulation, to take a currently relevant example – and now is or isn’t that time. It’s important that we can understand one another’s points of view without assuming we will all be able to agree.
Yet more fundamentally we need to accept the reality of perceptual diversity. How we see and hear the world is never fixed. This can seem a terrifying prospect, because it suggests we are all completely isolated individuals, but I think it should be ultimately seen as encouraging: it should deepen our compassion for our fellow humans. If I see the dress as blue and black rather than white and gold, I should use this opportunity to simply accept that someone sees things differently to me. This is the essence of tolerance.
[See also: What the Huxleys got wrong]