Where does icon collide?

In Charles Sanders Peirce's 1885 On the Algebra of Logic: A Contribution to the Philosophy of Notation, an icon is a sign that stands for its object by resembling it, one of three sign types alongside the index, which points to its object, and the symbol, which stands for its object by convention. A photograph, a diagram, or a scale model counts as iconic because its own qualities mirror the thing it represents. Here the referent is a relation between a sign and its object defined by likeness, not a painted holy image, a fading visual memory, or a small picture on a screen.[1]

Unit

One sign standing for its object by resemblance

Recovery means

Not applicable

Measured by

Identified by analysing how a sign relates to its object: by likeness, by physical connection, or by convention

Ulric Neisser's 1967 Cognitive Psychology named the icon: a very short-lived visual memory that briefly holds a nearly complete image of what the eyes just saw before it fades. Michael Coltheart's 1980 review Iconic memory and visible persistence refined the account and separated the distinct processes that partial-report experiments had grouped together. Here the referent is a fleeting internal store in a person's visual system, timed in milliseconds, and it has nothing to do with a sign type, a holy image, or a screen control.[2][3]

Unit

One brief visual trace, lasting a fraction of a second

Recovery means

The trace decays within a few hundred milliseconds unless attention transfers it onward

Measured by

Estimated by partial-report experiments that cue one row of a briefly shown display and compare recall against whole-report