Understanding the Role of Age and Fluid Intelligence in Information Search
Shari Trewin, John T. Richards, Vicki L. Hanson, David Sloan, Bonnie E. John, Cal Swart, John C. Thomas · 2012 · Proceedings of the 14th International ACM SIGACCESS Conference on Computers and Accessibility (ASSETS 2012) · doi:10.1145/2384916.2384938
Summary
This study investigates whether age or fluid intelligence is the more important factor driving differences in how people search for information in hierarchical web interfaces. The researchers recruited three groups: 14 younger adults with high fluid intelligence (YH, mean age 22), 19 older adults with high fluid intelligence (OH, mean age 68), and 22 older adults with lower fluid intelligence (OL, mean age 74). Fluid intelligence — the ability to reason abstractly and solve novel problems — was measured using the Letter Sets test. Participants navigated a three-level category hierarchy of 3,938 categories drawn from the UK eBay website, completing 32 tasks that required finding a specific item category within a 150-second time limit. The researchers tracked mouse movements, clicks, and eye fixations using a Tobii X120 eye tracker. Tasks varied in difficulty from easy (clear category path) to hard (category labels that did not obviously match the target item). By comparing younger adults with older adults matched on fluid intelligence (YH vs OH), and then comparing older adults with different fluid intelligence levels (OH vs OL), the study could disentangle the effects of age from cognitive ability.
Key findings
When younger and older adults were matched on fluid intelligence, there was remarkably little difference in search strategy. Both YH and OH groups made similar first click choices (73% vs 71% correct), fixated similar numbers of links, and showed no significant differences in re-clicks or mouse distance. The performance differences that did exist — younger adults completed 92.4% of tasks vs 77.6% for older adults, and were faster — were largely attributable to well-established age-related differences in perceptual and motor speed rather than different strategies. In contrast, comparing older adults with higher vs lower fluid intelligence (OH vs OL) revealed both performance and strategy differences. OL participants completed only 59.2% of tasks, re-selected previously clicked links twice as often as OH, were less willing to backtrack to the top level of the hierarchy, performed narrower searches, spent more time looking at the goal text, and had longer mouse paths before clicking. The OL group also made significantly more click errors on areas with no link target, possibly indicating motor skill differences correlated with fluid intelligence.
Relevance
This research has significant implications for accessible web design. It demonstrates that many age-related differences in web search performance attributed to "being old" are actually driven by fluid intelligence, which varies widely among older adults. This challenges the common practice of treating older adults as a homogeneous group in usability research and design. For practitioners, the findings suggest that the 150-second time limit alone was enough to turn age-related motor and perceptual slowness into task failure, even when strategy was equivalent — a powerful argument against time-limited interactions in web interfaces. The study also shows that users with lower fluid intelligence adopt compensatory strategies like using the mouse cursor as a memory aid, which has implications for cursor-dependent interface designs. Designers should ensure hierarchical navigation is forgiving of wrong choices, supports easy backtracking, and does not penalize slower exploration.
Tags: cognitive accessibility · aging · fluid intelligence · eye tracking · information search · mouse interaction · older adults · web navigation