PERCEPTUAL ISSUES IN DYNAMIC INTERFACES

Summary from the TLDR Design newsletter

Dynamic interfaces built with Ajax can change content without users ever noticing, because inattentional blindness, change blindness, and attentional gambling let even large updates slip past. In testing on a UK government site, users caught a content update but missed the menu expansion happening at the same time. Making changes bigger, brighter or animated, and placing feedback where users are already looking, keeps updates from going unseen.