Perceptual comparison speed: judging whether two shapes or letters are the same — physically, by name, or by category — in the tradition of Posner's letter-matching studies.

Same judgments are usually faster for familiar items because a single mismatching feature settles "different," while "same" requires verifying every feature.

Physical identity is fastest, name matching slower, and category or semantic matching slowest — each level adds a processing stage.

Rotation, mirror reflection, and visual similarity all add time; the task is a standard measure of perceptual speed in mental-abilities research.