100 Things: Every Designer Needs to Know About People

7. People See Cues that Tell Them What to Do With an Object

You’ve probably had the experience of encountering a door handle that doesn’t work the way it should: the handle looks like you should pull, but in fact you need to push. In the real world, objects communicate to you about how you can, and should, interact with them. For example, by their size and shape, doorknobs invite you to grab and turn them. The handle on a coffee mug tells you to curl a few fingers through it and lift it up. A pair of scissors invites you to put fingers through the circles and move your thumb up and down to open and close. If the item, like the door handle, gives you cues that don’t work, you get annoyed and frustrated. These cues are called affordances.

James ...