  The goal of this study is to expand our understanding of the relationships
between selected tasks, cognitive abilities and search result interfaces. The
underlying objective is to understand how to select search results presentation
for tasks and user contexts. Twenty three participants conducted four search
tasks of two types and used two interfaces (List and Overview) to refine and
examine search results. Clickthrough data were recorded. This controlled study
employed a mixed model design with two within-subject factors (task and
interface) and two between-subject factors (two cognitive abilities: memory
span and verbal closure). Quantitative analyses were carried out by means of
the statistical package SPSS. Specifically, multivariate analysis of variance
with repeated measures and non-parametric tests were performed on the collected
data. The overview of search results appeared to have benefited searchers in
several ways. It made them faster; it facilitated formulation of more effective
queries and helped to assess search results. Searchers with higher cognitive
abilities were faster in the Overview interface and in less demanding
situations (on simple tasks), while at the same time they issued about the same
number of queries as lower-ability searchers. In more demanding situations (on
complex tasks and in the List interface), the higher ability searchers expended
more search effort, although they were not significantly slower than the lower
ability people in these situations. The higher search effort, however, did not
result in a measurable improvement of task outcomes for high-ability searchers.
These findings have implications for the design of search interfaces. They
suggest benefits of providing result overviews. They also suggest the
importance of considering cognitive abilities in the design of search results'
presentation and interaction.
