  Visual highlighting can guide user attention in complex interfaces. However,
its effectiveness under limited attentional capacities is underexplored. This
paper examines the joint impact of visual highlighting (permanent and dynamic)
and dual-task-induced cognitive load on gaze behaviour. Our analysis, using
eye-movement data from 27 participants viewing 150 unique webpages reveals that
while participants' ability to attend to UI elements decreases with increasing
cognitive load, dynamic adaptations (i.e., highlighting) remain
attention-grabbing. The presence of these factors significantly alters what
people attend to and thus what is salient. Accordingly, we show that
state-of-the-art saliency models increase their performance when accounting for
different cognitive loads. Our empirical insights, along with our openly
available dataset, enhance our understanding of attentional processes in UIs
under varying cognitive (and perceptual) loads and open the door for new models
that can predict user attention while multitasking.
