Cognitive consequences of search

For some time now, the general goal of information retrieval (IR) has been to present a user with an optimally ranked set of results as quickly as possible. At first glance, things seem to be working well: users often find what they need on the first search results page, they do not have to create their own queries or read through multiple pages of text, and soon they may not even have to think of their own information needs. Researchers document success by showing reductions in time and amount of interaction, and increased user satisfaction, but do these measures really allow researchers to understand the impact of search?