Proceedings of the Third International Conference on Memory, 47. 2002. [ICOM 3; Valencia, Spain.]
The capacity of visual short-term memory was measured via a "flicker" technique, where an original and a modified image continually alternated. Each image was an array of simple items that sometimes contained a change. Observers were asked to detect this change.
For outlined rectangles that changed orientation, performance corresponded to a capacity of 5.3 items. However, capacity was over 15 items for rectangles changing contrast polarity or size, suggesting that these items were grouped into a single global structure, or constellation. Grouping also occurred for orientation when items had no local structure (i.e., were simple line segments).