Popularized by Don Norman, the Don of UX-as-cognitive-science, affordances are widely understood to be the opportunities for interaction visible in things. Look at a pair of scissors and see where your hands go. For Norman, an affordance is a design feature of an actual object, it’s something that can be seen by someone and recognized based on their past experiences.
Ok, these bird scissors are a tricky example. They really only make sense because you know what scissors are and how to use them. Also probably because you are familiar with decorative birds. This will be important later, but now let me give you a clear example of an affordance. What is a baby likely to do with this nippled bottle?
Norman cites psychologist James J. Gibson for the cool idea of affordances. Gibson’s work on vision centered on a bigger claim: the mind does not assemble a complete visual image and then act on it, instead pieces of the visual field go directly to separate processing departments. I love this idea because it contradicts the model wherein the mind is a homunculus at the controls of some giant robot with organic cameras for eyes. Also, it really speaks to my experience as an athlete, where I respond to things before I know what I’m looking at. Finally, it accounts for the human body as a messy pile of competing habits/instincts, which sounds a lot like real life.
So, to Gibson, an affordance isn’t a design feature. It’s actually a form of experience in the mind, or, even, a protocol for information processing put to use in the human nervous system. So when you design a sweet call to action button or an elegant, simple control device, you haven’t built an affordance. You’ve created something that may work as an affordance to a person.
There’s another key difference between Gibson’s idea and Norman’s powerful popularization of it. For Norman, the affordance is just that part of the design suggesting how a person might use the tool. The nipple of the bottle or the handles of the scissors. But for Gibson, humans also see sharp blades on scissors and the round reservoir for fluid in a bottle. Affordances are potentials for interaction between the object and all kinds of other things. These scissors might work as a decorative item or a letter opener. The bottle might work as a paperweight or a ball. MacGyver is just really good at seeing affordances.
You could write out a near series of examples on this theme, where people see certain potentials in objects that might not match reality very well at all. Bananas, for example, can actually be opened by cracking the peel open by pulling the fruit’s two ends together really fast. A pen with barely any ink left certainly looks like a pen — the affordances are there — but you can’t write a single lousy word with it. Dental floss, to a prisoner, is string.
To recap: affordances develop over the lifetime of a person, are only indirectly about the objective properties of an object, and have to do with potential interactions between any part of an object and its environment (or, hell, things you brought in from across town).
What are the affordances of a surfboard? If you’ve never seen one before, it would probably not occur to you that you could swim it into the ocean’s waves and then hop up on it and ride those waves back towards shore. That affordance would just not exist.
Now, once you’ve been using a surfboard for a long time, you might start to see the affordance of “put my feet on this thing and ride down slopes” in other things. Like a plank of wood with wheels on it.
A plank of wood with wheels on it would have rolled down hills in a world without surfing, but the affordances developed in surfing eventually guided some people into doing things with a skateboard that had not been done before. (This story brought to you by the 2001 documentary Dog Town and Z-Boys which I must have watched in about 2001.)
For design today, what all this means is that “affordances” are conventions that specific real people have learned from other things they’ve done in their life (moreso things they’ve done recently than once upon a time). This means that affordances continue to change and so the things specific real people are ready to do with the products you build for them depend on what they’ve been using recently. So copy the things they know how to use. (Copy mainstream systems, but only if people get how to use them!)
Innovation must build from existing habits, though it can combine them creatively. Good news: the domain of convention that design is lifting from is as wide as the universe of affordance-patterns in the nervous systems of the target market. People using your product probably know how to make coffee and fold paper and take photos. Bad news: if you find an affordance that is relevant to you, then your skateboard-style controller had better act like a real skateboard or the affordance-pattern will be a liability more than an asset.
Is the theory of affordances true? Does Gibson’s theory of vision really accord with human cognition? Is Norman right that these affordances relate to mental models of things and that guides how people use things? Is all of this poppycock?
Good questions. To be considered another time.