Some search topics pose little challenge to a search system (“easy”), and some are more difficult (“hard”). We investigated the relationship between one measure of searcher behavior (queries entered per minute), and one measure of system response (the average length of the lists returned) for topics at two levels of difficulty. Specifically, each of 36 participants searched for information about 12 topics: 2 that were “easy” and 10 that were “hard”. We find that when working on easy topics, searchers entered queries less frequently over the course of the search. We also find that lists of retrieved items, as returned by the system, were longer on average for easy topics. We propose that these findings may be useful in designing interactive search systems capable of “awareness” of search difficulty.