What's the difference between the terms "affordances" and "signifiers"?

Question

I do not understand the difference between the concepts affordances and signifiers. I am given the following definitions:

Affordances: "Relationship between properties of an object and the capabilities of an agent that provide clues to the use of an object. Affordances must be perceivable / visible to be effective"

Signifiers: “Any mark or sound, any perceivable indicator that communicates appropriate behavior to a person”

Could someone explain with examples? Is it that signifiers signal how an object can be used and affordances is how it actually can be used? Rereading that last sentence I realize it made no sense, what I meant is do signifiers convey how an object is supposed to be used and accordance is more of a matter of reality in how it can be used.

Answer 1

Affordances are what an object can do (truth). Perceived affordances are what one thinks an object can do (perception). Signifiers make affordances clearer (closing the gap between truth and perception). Signifiers often reduce number of possible interpretations and/or make intended way of using an object more explicit.

A grey link on the screen might afford clicking (truth). But you might perceive it just as a non-interactive label (perception). Styling it as a button (background, shadow etc.) is a signifier that makes it clearer that the link can be clicked.

Answer 2

Affordance has to exist, it is an implicit property of an object. Let me cite Norman (who is citing James J Gibson):

...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

That's exactly the point, signifier without affordance is a mistake (a fixed door with a big PUSH HERE text) but affordance can exist without signifiers. One main point of UX design is to introduce signifiers to make affordance visible.

Norman used that word to identify perceived qualities of an object, this led to some confusions because now those terms slightly overlap but the central point is still the same: affordance is an implicit quality (visible or invisible) of an object to be used. When an object has not such perceived quality then you introduce signifiers to make it clear.

Let's imagine a secret door. According to Gibson it has the affordance to be—for example—pushed to be open even if you carefully tried to make it invisible and to remove that perception. Instead, according to Norman's definition, it lacks of affordance because its usage is not perceived.

Now imagine a normal door without handles. Because of materials, position or expectations (for example because it's at the end of an empty corridor) it has a perceived affordance. If it's not clear enough then you add a signifier, for example, a Push here plate.

Signifiers are not used just to make affordance visible, citing (again) Norman:

Consider a bookmark, a deliberately placed signifier of one's place in reading a book. But the physical nature of books also make them an accidental social signifier, for the placement of the bookmark tells the reader how much of the story remains.

To summarize in one line what I tried to explain in such dump of text:

The perceivable part of an affordance is a signifier, and if deliberately placed by a designer, it is a social signifier.

Answer 3

Don Norman's definition of 'affordance', from "The Design of Everyday Things":

An affordance is a relationship between the properties of an object and the capabilities of the agent that determine just how the object could possibly be used. A chair affords (“is for”) support and, therefore, affords sitting. Most chairs can also be carried by a single person (they afford lifting), but some can only be lifted by a strong person or by a team of people. If young or relatively weak people cannot lift a chair, then for these people, the chair does not have that affordance, it does not afford lifting.

The presence of an affordance is jointly determined by the qualities of the object and the abilities of the agent that is interacting. This relational definition of affordance gives considerable difficulty to many people. We are used to thinking that properties are associated with objects. But affordance is not a property. An affordance is a relationship. Whether an affordance exists depends upon the properties of both the object and the agent.​

Contrast that with his definition of 'signifier':

To be effective, affordances... have to be discoverable - perceivable. This poses a difficulty with glass. The reason we like glass is its relative invisibility, but this aspect, so useful in the normal window, also hides its anti-affordance property of blocking passage.

As a result, birds often try to fly through windows. And every year, numerous people injure themselves when they walk (or run) through closed glass doors or large picture windows. If an affordance or anti-affordance cannot be perceived, some means of signaling its presence is required: I call this property a signifier.

So in plain English, an affordance is something that can be done with a thing by a certain person. For example, a mug has the affordance of "pickupability" for someone who can pick things up. Norman takes pains to emphasize that affordance are person-specific, as in his example with the heavy chair above.

The presence or absence of signifiers determines how easy it is for a person to understand that thing's affordances. For instance, a door handle is a signifier which allows me to intuit that the door is meant to be pulled (not pushed). In contrast, if it just has a brass plate where a handle would normally be, I can intuit that the door is meant to be pushed.

Answer 4

There's a lot of misunderstanding about what affordances are. The definition I've come to from study of Norman and Gibson is that they are properties of things.¹ They are not objects; a door is not an affordance. They are not actions; pushing is not an affordance.

Affordances are properties: hollowness, heaviness, solidity, etc. We perceive these properties and gain an understanding of what we can do with the object from them.

I'm less familiar with signifiers but by your definition they seem to be a subset of affordances, those that are intentionally created as marks or sounds. Signifiers are a type of affordance, but there are affordances that are not signifiers: flexibility, shininess, hollowness, twistability, etc.

¹: I've proposed that "thing" can be not just physical and digital things, but also organizations, ideas, and such.

Answer 5

By definition, an affordance is a situation where an object’s sensory characteristics intuitively imply its functionality and use. — Crowdcube

The signifier, on the other hand, is the pointing finger, a sound, an image or a word, and it's related to semiotics.

Perhaps you mean the difference between an "affordance" and the "signified". The signified is the concept formed within your mind by the signifier.

An affordance is more like a potential reality. In this regard, it's quite the opposite of a signified object - when talking about affordances, an object can represent everything with regard to functions and usability, whereas a signified object is already a mental representation, a definite status built by your conscience with regard to a certain object.

Affordances require an open mind and the will to interpret and take creative initiatives when interacting with the outside world, while a signified object implies following your instincts and seeing things as you already think they are.

Affordances are only the values we give to a certain object, like a sum of properties and functions. A signified concept is the projection of the object itself into our mind.

Answer 6

I think Don sometimes makes life unnecessarily complicated with his rather loose use of terminology !

With these two terms we are hopping between two aspects of psychology.

1. The fairly instinctive world of cognitive psychology to which affordances belong:- tell someone to pick something up and they have an instinctive sense of whether it's too big or not- this is to do with the thing in the physical world and some fairly hard wired mental processing.

and

2. the world of social psychology to which signifiers belong.

To take his bookmark example: the bookmark by virtue of shape and size affords being placed in a book as a marker (in a way that an object which was a metre long metal cube wouldn't). This is to do with the physical characteristics of the object

It's also a 'social signifier' because that's its purpose: telling the reader where to come back to in the book. That's what it does because people like to get back quickly to where they are in the book.

There are other ways of solving the problem, such as bending over the corner of the page (which is an affordance of the physical page).

So the use of the bookmark (especially say a nice leather one with a pleasing graphical design) signifies a lot about the reader (they have started reading the book; they like pleasing graphical design; they value books and don't turn pages over), to another human being who might come across the book.

And the full article is here:

http://jnd.org/dn.mss/signifiers_not_affordances.html