Reducing the Search Space on demand helps Older Adults find Mobile UI Features quickly, on par with Younger Adults

As mobile user interfaces (UI) become feature-rich, navigation gets more complex. Finding features quickly starts demanding information-intensive strategies for decision-making—which can be challenging for older adults. Older adults examine fewer details, requiring fewer cognitive resources, when searching for information with a large number of alternatives. In this paper, we first systematically examine various ways to convey a reduced feature space. Visually emphasizing three relevant options helped older adults find a specific feature more quickly—on par with younger adults. Older users were more efficient when options were highlighted along with their context or with a weighted zoom than when just highlighted, and they also preferred these two the most. We then present Nav Nudge, an interaction technique that uses voice input and large language models to visually reduce the feature search space on demand—and discuss how older adults use it within a mobile map application.