Which representation shows the areas of the screen where users have spent the most time looking?

The correct choice is a heat map because it visually represents areas on a screen where users have focused their attention, typically by using a color gradient to indicate the intensity of gaze and duration. In a heat map, colors such as red or orange usually indicate regions where users have spent the most time looking, while cooler colors like blue suggest less attention. This form of representation is particularly useful in UX design as it helps identify which parts of a design draw users' attention and which areas may be overlooked, providing insight into user behavior.

Other representations like fixation maps and gaze plots offer valuable but different types of information. A fixation map shows specific points where users' gaze has paused, highlighting those points but not necessarily providing an overall view of time spent across the entire interface. Similarly, a gaze plot details the sequence of eye movements and fixations, tracking the path a viewer's eyes take but lacking the aggregated pictorial representation of attention duration that a heat map provides. Attention maps, while similar to heat maps, may focus on predicted visual attention based on design elements rather than actual user gaze data. Thus, heat maps are particularly effective for analyzing user engagement and optimizing design based on where users focus their attention over time.