Signifiers, Not Affordances
Donald A. Norman

Nielsen Norman Group and Northwestern University | [e-mail]

References

trail or trace of previous behavior: desire lines, as these are called in architecture and city planning—when the trails made by people’s footsteps across fields indicates their desire for paved paths.

I call any physically perceivable cue a signifier, whether it is incidental or deliberate. A social signifier is one that is either created or interpreted by people or society, signifying social activity or appropriate social behavior. Thus, although there are many possible signifiers of wind speed and direction, including flags, the movement of grasses or tree leaves, or traveling debris, if the signifier is a flag, it is also a social signifier—people placed that flag in its location, presumably for a reason (which may have nothing to do with providing an indication of the wind).

It’s time for a review. As times and technologies change, as we have moved from individual to group, social, and even cultural computing, and as communication technologies have become as important as computational ones, how well have our design principles kept up?

One of our fundamental principles is that of perceived affordances: how we know what to do in novel situations. That’s fine for objects, but what about situations? What about people, social groups, cultures? The answer is the same, yet different. Yes, there are still perceived affordances, constraints, and conceptual models, but there’s more. There are trails. There are behaviors. We know how to behave by watching the behavior of others, or if others are not there, by the trails they have left behind. As we move from the world of stand-alone objects to social structures, complex, intelligent products, and a heavy dominance of services, then new principles are needed.

Powerful clues arise from what I call social signifiers. A “signifier” is some sort of indicator, some signal in the physical or social world that can be interpreted meaningfully. Signifiers indicate critical information, even if the signifier itself is an accidental byproduct of the world. Social signifiers are those that are relevant to social usages. Some social indicators simply are the unintended but

informative result of the behavior of others. Let me illustrate.

Suppose you are rushing to catch a train. You know the train was scheduled to depart soon. You run across the city, run up the stairs in the train station, and rush on to the platform. But there is no train. Did you miss it, or perhaps it simply has not arrived yet? How can you tell? The state of the platform serves as a signifier. People milling about? The train has not arrived. An empty platform? Oops, you missed it. This is an example of an incidental, accidental signifier. It isn’t completely reliable, working better in small towns with only occasional trains than in crowded cities where many trains use the same platforms, but that is the nature of signifiers: often useful, but of mixed reliability.

Social signifiers, such as the presence or absence of people on a train platform, painted lines on the street, the trails that signal shortcuts through parks or across planted areas, are examples of signaling systems. Signals come in many forms, sometimes naturally evolved, sometimes conventions of culture. Cues carry evidence, sometimes completely unintentional, as in the emptiness of the train platform. A flag’s fluttering in the wind is a clue to wind direction and speed, usually unintentional, but nonetheless useful evidence to the observer. Sometimes the evidence is a

Signifiers, Not Affordances 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 confusion and a gold mine