Affordance is a real good tool to use (or try to use) in design, but is poorly understood. As its a quiet Friday afternoon I thought I’d see if I could remember what it was all about.


When Emma, my daughter, was one and a half or so I had a modem under my computer that had a large raised area on it. And without any hesitation when she came across this modem she tried to press this area with her small fingers. Why would she do this? What was special about the raised area? There were other areas of the modem that could have been pressed … why this bit? Well, it ‘afforded’ pressing, or to put it another way it looked like it was for pressing.

Emma was just making some words then, but hadn’t any real understanding of language or cultural conventions. She just knew it was for pressing…even though actually it was just decoration

Why? Why would a small child do this? Well, the story starts back in the 50’s when a psychologist called JJ Gibson was investigating depth perception and the way that fighter pilots worked out how to land their planes, and how they used their vision. He came to a distinctly anti-cognitive solution which was that they did not ‘model’ the world in their heads to compute, process and predict what was going on. He said that the pilots used the ‘knowledge in the world’ to create a relationship between themselves and things in the world to get them down.

All a bit wooly, but it was the era of behavourists and anti-cognitive was good. But his ideas stuck, and the notion that an affordance was about a natural relationship between humans and the world has held on quite strongly. So, Emma doesn’t need to ‘model’ the modem and its decorative button, the afordance stems directly from the relationship between the individual and the world artifact … knowledge is in the world not the head.

Ok, so where does that get designers? Well, it means if you design something that looks like it should be, and consider the relationship, you get good design. And if you design something that doesn’t look like it should be then its poor.

Chairs are the big example. A chair affords sitting in, but apriori theres no real reason it should. Its just that we as humans have a particular shape and the designer has made it to reflect that ‘fit’. Thats why chairs are good or not, and afford sitting in or not. Chairs afford other things to small children … climbing on, hiding under. And small chairs afford sitting on to children, and other things to adults if need or intention arises … like standing on for example. Its about the relationship, needs and intentions and about things satisfying them. We cant have models of everything in the world, we have to interpret the world as it is.

Another famous example is the door handle. A door handle affords pulling. But how many of us have pulled one only to find that under it is a sign that says push? Poor design. The handle ‘is for’/affords pulling. Only after we have reacted at a behavoural level do we consider and reflect (and fume!) when we realise we need to push.

And the internet? Well, some would say that if a thing aint real then its a ‘percieved’ affordance not a ‘real affordance’. Buttons on the screen aren’t the same as ‘buttons’ on my old modem. I dont get this because the reality is that you have a perception (arrangement-of-pixels-as-button), and you have an interaction device (mouse) and therefore there is a relationship. I think JJ Gibson would press the Big Red Button, and agree that these affordances are just as real as any physical object, and we can have relationships with them as we can with the ones made of plastic or metal.

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