Signifier

Don Norman introduced signifier to clean up a mess he had made. The Design of Everyday Things borrowed affordance from perception psychology, designers took it to mean the visual hint rather than the action possibility, and by the 2013 revision he had split the two: the affordance is what the thing allows, the signifier is what tells you so. The distinction earns its keep because on a screen the possibilities are all identical. Glass affords touching, everywhere, equally. Every difference a reader can perceive between a button and a paragraph is drawn, which makes the signifier the entire design surface.

A signifier is anything perceivable that communicates where the action goes: the raised edge and fill of a button, the underline under a link, the grip dots on a drag handle, the cursor that becomes a hand or a resize arrow, the partial row peeking at the bottom of a list that says the content continues, the chevron that says this opens. Some are physical inheritances (a door’s flat plate says push), most are pure convention, and convention is not a weaker kind of signifier. It is the strongest one available, because the reader arrives already fluent in it. That is why redesigning a link to not look like a link is expensive in a way that has nothing to do with taste.

Norman’s own examples run the other way too. Worn paint on a door, a footpath beaten across a lawn, a queue of people at a counter: none of these were designed to communicate anything, and all of them tell you what to do. Interfaces have the same accidental signifiers, and they are usually bugs. A cursor that stays as an arrow says a control is not clickable. Text with no underline says it is not a link. Uniform padding says two elements are the same kind of thing. Readers act on these signals whether or not anyone intended them.

Which is what makes the failure worth naming precisely: an affordance without a signifier is invisible, and a signifier without an affordance is a lie. Flat design spent years rediscovering the first (borders and fills were doing work nobody had costed), and the second turns up as a false affordance every time text is styled like a link but does nothing, or a static image is dressed as a play button. Hover only signifiers are both failures at once, since roughly half of readers have no pointer to reveal them with.