The art of thinking · 2 · Perception and attention

Change blindness

German: Veränderungsblindheit

In cognitive psychology, change blindness is the failure to notice large changes in a visual scene when the change coincides with an interruption — a blink, an eye movement, a blank screen, a cut or a page turn — so that no motion signal draws attention to it.

Cognitive psychology
Attention
Perception

In one sentence

Change blindness is failing to notice large changes in a scene when they happen during an interruption such as a blink, a cut or a page turn.

Example

In a revised operating manual the maximum load in a table changes from 800 kg to 600 kg. Readers who know the old edition turn to the page and read on without noticing the new value.

What the research shows

Ronald A. Rensink, J. Kevin O'Regan and James J. Clark (1997) alternated an original and a modified photograph with a brief blank in between (the flicker paradigm). Observers took a long time to find even large, repeated changes; a verbal cue made identification much faster, and changes to objects of central interest were found faster. The authors concluded that observers do not build a complete, detailed representation of a scene and that attention is needed to perceive a change. Daniel J. Simons and Daniel T. Levin (1998) showed the effect in a real interaction: when an experimenter asking for directions was replaced by another person while a door was carried between them, about half of the pedestrians did not notice the switch.

Evidence status

Change blindness is robust across flicker, cut and real-world paradigms. How much of a scene is stored without attention, and whether people fail to see or fail to compare, is still discussed. Most observers believe they would notice such changes (sometimes called change blindness blindness), so self-reports of noticing are unreliable. Changes that produce a visible transient — motion, flashing, a new element appearing in view — are noticed far more often.

How it applies

Revised documents, new editions, updated values on a screen and software releases change information that readers believe they already know. Without a cue, a change may not be noticed. Change bars, revision lists and change notices are the practical answers discussed in the glossary “Applied cognitive psychology for information use”; on the system side, versions and changes are managed through management of change (MOC). Marking a change does not by itself ensure that safety-related changes reach the people who need them.

External references

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