Modern search systems often meet their users' information needs, but when the system fails, searchers struggle to formulate effective queries. Query suggestions may help, but research suggests these often go unused. Although much is known about how searchers scan results pages when assessing relevance, little is known about the processes searchers use when struggling to reformulate queries. Investigating how searchers overcome query difficulties, and how search systems help and hinder that process, requires enquiry into the cognitive procedures searchers use to select words for queries. The purpose of this paper is to investigate one cognitive process involved: semantic priming of words in memory. A framework for conceptualizing the role of semantic priming in search interaction is presented, along with results from two experiments that applied research methods from cognitive psychology, in an investigation of word selection and subsequent search for selected words. The results show that word selection activates related words in memory and that looking for a selected word among related words is effortful. The finding suggests that semantic priming may play a role in the difficulties people experience when reformulating queries. Ideas for continued development of semantic priming methods and their use in future research are also presented.