The images' textual descriptions from experts and the general public, subject headings and social tags, are provided to facilitate image search process. Search tactics represents a series of search choices and actions with the textual descriptions provided on the systems during the search process. However, integration of different textual descriptions for image finding have rarely been investigated. This study investigates how two types of textual descriptions in relation to subject headings and social tags affect user' search tactics. Thirty-six participants were recruited for this study. Multiple methods were employed to collect data, including questionnaires, interviews, and eye-tracking analysis. Eliciting participants' viewing behaviors, this study benefits our understanding of different search tactics of users and provide adaptive mechanisms to fulfill their search needs. The results of this study provided four guidelines for practitioners when designing adaptive image search interface to fulfill users search tactics.