Internet trolling involves making assertions with the aim of provoking emotionally heated responses, all while pretending to be a sincere interlocutor. In this paper, I give an account of some of the epistemic and psychological dimensions of trolling, with the goal of better understanding why certain kinds of trolling can be dangerous. I first analyze how trolls eschew the epistemic norms of assertion, thus covertly violating their conversation partners’ normative expectations. Then, drawing on literature on the “explore/exploit trade-off,” I argue (...) that trolling is a kind of exploratory behaviour. Specifically, it involves exploring the consequences of violating an interlocutor’s expectation that one will follow the epistemic norms of assertion. To defend this account, I argue that it explains various facts about trolls and the kind of pleasure they get from their activities. My account provides a deeper understanding of why trolling can be dangerous: namely, it explains why certain trolling behaviours contribute to radicalizing people into extremist or hateful ideologies, as well as why online platforms where trolls run amok gradually become polluted with extreme, hateful speech. (shrink)