Don’t Pull on a Door Marked Push! (Affordance is not the same as affordable!)

If you came up to a door that had a handle on it, what would you do, if there were no sign on it?

You’d pull on the handle. Of course you would! It’s only when there’s confusion about doors, we have to label them push or pull. (Okay, some of you are thinking ‘aha, I’d look at the hinges’ and, indeed, some of you would – but most of us would just pull on that handle.)

This is affordance, where “the physical characteristics of an object or environment influence its function” (Universal Principles of Design; Lidwell, Holden and Butler; Revised edition, 2010)

See a door handle? Pull on it. See a door plate – you’ll push it. Ever wonder why Lego blocks don’t come with instructions? Because they only afford a certain set of composition actions – the design of the shape tells you how to use it.

By taking advantage of this property, we can reduce the amount of instruction that we have to give. If the purpose of the object is assisted by its construction and design, in terms of the user, then we will immediately achieve better and more effective use when someone does come to use it. We can even borrow the affordance of an object and use it somewhere else, building on our natural disposition to use it in a certain way. Ever wondered why graphical user interfaces (GUIs – the way that you interact with modern computers and devices) have button images on them? People know how to use real buttons – they stab it with a finger – and this, transplanted to the GUI domain, allows the user to reuse this familiar knowledge and turns what should be something complex (I’d like you to engage any of the pixels in the range (200,100)-(250,15) with your finger and apply light pressure) into ‘stab!’ without having to write one word of explanation.

From a teaching perspective, when we do develop materials to support our teaching, we implicitly use affordance all the time. Those ‘fill in the blanks’ spots we leave? There’s only one place to write and that place has a context inside the knowledge of the current sentence. Have you ever wondered why government forms have ‘do not write in this space’ or ‘for official use only’ in spaces? It’s because when we see spaces – we want to write in them. That’s what spaces are for? If you leave space around your printed lecture notes, you are saying “Please write on me!”

For me, this is why those ‘scratch-off the silver bit’ cards are so easy to use. You want to scratch it off – you’re (pardon the pun) itching to do so. If your rubric simply explains that you have to read the question and scratch off only one, that’s it. No complicated ‘COMPLETELY FILL THE CIRCLE WITH 2B PENCIL’ instructions or ‘tear off this strip after you’ve written down an answer’ – and no handwriting problems.

When we do try to take advantage of affordance, we have to make sure that the students we’re teaching are going to understand what we mean. If we’re using borrowed affordance, like the GUI buttons, we have to make sure that they have the original knowledge. The best way to test that you have the basics right is to give it to a colleague, without instructions, and watch what they do. Your own interpretation of your materials is biassed by your cognition. You know what you’re supposed to do – rather than listening to the material to see what it wants you to do. When your colleague picks up your quiz, looks at it, and starts joining dots on your scatter plot – it may be a sign of lack of coffee or no sleep, or it may be a sign that this is what your work is screaming at people to do.

I’d love to hear from people if they have examples of work that they think really exemplifies this.

One Comment on “Don’t Pull on a Door Marked Push! (Affordance is not the same as affordable!)”

  1. Alex H says:

    Well, there’s a box here that’s asking me to leave a reply. I guess I’d better type something into it…

    Simple metaphors are seductive; they encourage us to suspend our critical faculties. Lego blocks actually do come with instructions nowadays. There’s precious little in a modern GUI that literally looks like a button–we (you and probably everyone reading your blog) can handle the various icons on our screens simply because we’ve been habituated to them since many years ago.

    I’ve got to admit that the door example is good though.


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