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Looking at the UX principles that mozilla use as keywords to tag bugs in bugzilla it looks like ux-affordance and ux-discovery are very similar:

ux-affordance — controls should visually express how the user should interact with them. [Source: Norman]

ux-discovery — users should be able to discover functionality and information by visually exploring the interface, they should not be forced to recall information from memory. (This is often the nemesis of ux-minimalism since additional visible items diminish the relative visibility of other items being displayed). [Source: Nielsen]

Are these just two ways of looking at the same problem, or are there UX issues that would fall under one principle but not the other?

Update:

Perhaps the tag-wiki definitions on this site could be updated based on the responses to this question. They are currently:

Affordance is a property of an object that naturally indicates how the object can be used.

And for discovery:

the process by which a user learns what a program can do through affordances in the UX.

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    +1 It's good when meta questions like these about usability and UX are brought to light in the forum. I will give users of this forum a greater understanding of what a poster means when she uses these terms.
    – AndroidHustle
    Commented Jul 31, 2012 at 13:44
  • I think the definition of "ux-affordance" should probably be updated to say "controls should observably express...", given that affordance is not merely visual.
    – zzzzBov
    Commented Jul 31, 2012 at 17:32
  • "I will give"..? no, that's supposed to be "It will give"... =P
    – AndroidHustle
    Commented Aug 5, 2012 at 1:10

4 Answers 4

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+50

According to CodeAcademy, potentials for interaction are collectively called the affordances of an object. The visual cues or other aspects of an object that a designer uses to indicate potential and intended affordances of the object are called signifiers.

"The concept of 'affordance' has captured the imagination of designers. The term was originally invented by the perceptual psychologist J. J. Gibson to refer to a relationship: the actions possible by a specific agent on a specific environment. To Gibson, affordances did not have to be perceivable or even knowable -- they simply existed. When I introduced the term into design in 1988 I was referring to perceivable affordances. Since then, the term has been widely used and misused. The result has been confusions and a goldmine for academic scholars who get to write learned articles about the true meaning of the term."

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    Thank you. Signifiers is a really useful concept.
    – Sam Hasler
    Commented Dec 11, 2019 at 10:44
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    @moot, yes Don Norman & etc. have changed the definition of affordance, splitting out the actual provision of usability and the indication of usability in a more useful and accurate way. It does make sense as long as you look at what Don Norman is trying to achieve - a usefully precise design language. To quote Edsger Dijkstra, "The purpose of abstraction is not to be vague, but to create a new semantic level in which we can be absolutely precise". It sucks for me and you since half the literature is now obsolete, but I suspect that this train has left the station, and we just have to adapt.
    – Medievalist
    Commented Dec 12, 2019 at 17:08
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Affordance is related to the object itself. Eg: A button looks clickable.
enter image description here

Discoverability is related to the product/solution. Eg: An image-manipulation toolbar shows all features it is possible to use when you want to work with an image.

enter image description here

A physical example:
If you walk down a corridor, then the affordance of the door-handles will "tell you" how it is possible to interact with each door. (Push, pull, turn, lift etc). But the labels of each door will tell you what you can find behind each door.

enter image description here
Discoverability:
enter image description here - enter image description here

Affordance:
enter image description here

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    Affordance describes a relationship between the object and the user, and thus always depends on what the user/agent can do with the object. It's not a static indicator. What you describe is signifier.
    – Boghyon Hoffmann
    Commented Dec 16, 2019 at 11:42
  • OK. So the question was about the difference between "affordance" and "discovery", and how these concepts are used at Mozilla. You bring in "Signifiers". A term that wasn't widely used back in 2012. ("Signifiers" got attention when Norman brought up some clarification in his 2013-edition of "The Design of Everyday Things"). If you look at the original question and how the two terms were defined by Mozilla, you'll see that the answer actually answers the question. Whether Mozilla should have used other terms, that's another discussion, but this is what they actually tried to describe. ;-)
    – Jørn E. Angeltveit
    Commented Dec 17, 2019 at 14:43
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They're definitely different principles. Affordance aids discovery, but discovery isn't about the visual look and feel at all; it's not even about expressing what a single control does.

Say you have a delete button, it's red clearly 3D, depresses when you press it, just begs to be touched, and has a big trash can icon on it with the word "DELETE" written clearly on it. Very good affordance. But say that delete button is hidden behind 3 menus, one of which requires an uncommon long-press action. It's not discoverable. But is that a bad thing?

A philosophical difference between Affordance and Discoverability is that pretty much everything should have the best Affordance you can give it. Discoverability is something you have to prioritize; maybe you want that delete button to be hard to find.

See The Myth of Discoverability:

All things can not be easily discoverable because everything is limited. You have limited screen real estate, users have limited attention spans, and abilities to perceive or understand things. Therefore, all design for people is a zero-sum game: tradeoffs must be made and priorities must be set if there’s any hope of a good outcome for customers.

You have to prioritize and make common/important tasks the most discoverable. It's okay for less-common things to be harder to find; a good design still makes it possible to find those features, but leaving destructive features on the front page where they can accidentally be applied is not good for users.

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I would say that they are two sides of the same coin.

Affordance is, as you quoted, designing controls in a way that they by themselves convey to the user how the user should interact with them. A common example is a hammer, that has a grip friendly handle and a heavy head, a natural instinct would be to smack down on something with it.

Discoverability is more of a situation that can involve a set of controls that should be easily accessible when performing a task. Bringing back the hammer analogy it could be a toolbox that is includes everything that a user needs for building a house. It's clearly labelled and accessible and suitable for the situation.

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    see my answer above. Affordance is what a thing can be used to do, so a handle can be grasped, a hammer can drive or pull nails, etc.. Signifiers are the design elements that convey the information of what the affordances are, like the shape of the handle, the curvature of the hammer's claw, or even written directions glued to the object. Discoverability is how well signified the affordances are - do you naturally put your hand on the handle, or do you have to figure out where to put your hand by reading a poorly written, confusingly placed sticker?
    – Medievalist
    Commented Dec 12, 2019 at 17:15

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