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.