Summary: Significant changes in a web page can remain unnoticed when they lack strong cues, due to the limitations of human attention.
In usability testing, we often observe users who overlook a change on the screen that the designers thought would be obvious and highly noticeable. As always in usability, if you worked on a design, then you know what to look for, where to look for it, when it will appear, and what it means . So yes, it’s obvious to you and you wouldn’t miss the appearance of an important message or data object when you review your own design. But users often do. Why? Because of change blindness, which is a million-year old fact of human (and protohuman) perception, and not likely to go away any time soon.
So what is change blindness? In Alfred Hitchcock’s Psycho , one of the most famous movies of all time, detective Arbogast looks at Norman Bates’ house projected on a dark cloudless sky. The camera moves back to the detective’s face, and follows him as he starts walking toward the house. The scene is still dark, but the sky has suddenly become full of clouds.
Whether the change in the sky’s texture was intentional (perhaps Hitchock’s subtle warning for what was to come) or a continuity error, chances are that most viewers won’t notice it. Motion pictures often have small inconsistencies like this from one scene to the next — changes in the background, in the actors clothing, makeup, or positions, but these get ignored when they are made during cuts between scenes.
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