People use search engines to find answers to questions related to their health, finances, or other socially relevant issues. However, most users are unaware that search results are considerably influenced by search engine marketing (SEM). SEM measures are driven by commercial, political, or other motives. Due to these motivations, two questions arise: What information quality is mediated through SEM? And how is collecting documents of different quality affecting user knowledge gain? Both questions are not considered by existing models of information behavior. Hence, the doctoral research project described in this paper aims to develop and empirically test an information search behavior model on the influences of SEM on user knowledge gain and thereby contribute to the search as learning body of research.