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Which Changed shows a set of items, alters one, and asks which. It is a change-detection task, and it demonstrates change blindness directly — people routinely miss substantial changes when the change happens during a brief interruption.
Study the set of items.
The display is briefly interrupted.
The set returns with one item changed.
Identify which item changed.
Sets grow and changes become subtler.
Change detection and the comparison between a remembered set and a present one. The comparison is where errors happen, not the storage.
Name each item during the study phase. A verbal list is easy to compare against; a visual impression is not.
Scan in the same order both times. Comparing in a different order is where misses come from.
Note colours and counts specifically — those are the attributes that tend to change.
Compare category by category if the items group naturally.
The failure to notice large changes between two views when the change is masked by an interruption. It is one of the most striking findings in attention research.
Without it, the change itself produces motion that grabs attention automatically. The interruption removes that cue and forces genuine comparison.
Missing Object removes an item. Here an item changes, which is harder because the count stays the same.
Verbal labelling. It converts a hard visual comparison into an easy list comparison.