Task descriptions in usability tests: A source of split-attention

Abstract

Having to switch between task descriptions and the interface during a usability test induces cognitive load for participants and increases time on task. An explorative study is reported, showing a large individual variability in how often and for how long participants returned to task descriptions. They returned to descriptions at least once in 80% of all cases (Max=13, Median=2), spending up to 147s re-reading the description (Median=7s). This constituted up to 67% of the total time on task. Practical implications regarding the design of task descriptions and for summative usability testing are sketched.