More and more, people are abandoning the active pursuit of news, assuming instead that important information will be pushed to them via their social media networks. This approach to news makes people susceptible to the vast amounts of misinformation online, yet research on the effects of this kind of engagement is mixed. More research is needed on technology incidental learning effects, defined as changes in knowledge, attitudes, beliefs, and behaviors as a result of being exposed to information while pursuing goals other than learning (e.g., entertainment). In this study, we examined how 51 college students responded to incidental exposure to accurate and inaccurate COVID-19 information delivered via a simulated social media environment. Participants' verbalizations during think-aloud protocols indicated numerous mental processes including cognition, metacognition, epistemic cognition, motivation, and emotions. Positively valanced mental processing was more often expressed with accurate COVID-19 information and negatively valanced mental processing was more often verbalized with misinformation. Negatively valanced evaluations of knowledge claims and sources predicted less engagement with COVID-19 misinformation posts. However, in many cases the relations among verbalized mental processing and behavioral responses were complex or nonobvious. For example, participants' positive metacognition and epistemic cognition verbalizations decreased their likelihood of engaging with accurate COVID-19 information, whereas positive interest was associated with an increased likelihood of engaging with misinformation. Our findings have implications for how to accurately infer people's beliefs and intentions from their social media behaviors and how to design interventions to help people be more active and thoughtful consumers of online information.