This Element aims to better understand the role of the internet in the radicalization process, focusing on how online factors contribute to self-radicalization. Specifically, it examines the neurocognitive process of online radicalization by analyzing the impact of terrorist and extremist propaganda videos on individuals' cognitive empathy using electroencephalography (EEG). Ultimately, this research aims to provide a more comprehensive understanding of online radicalization and the psychological effects of exposure to extremist content on the internet. This Element explores the role of the internet in the radicalization process, focusing on how online factors contribute to self-radicalization. It analyzes the neurocognitive impact of terrorist propaganda videos on individuals' cognitive empathy using electroencephalography, providing a comprehensive understanding of online radicalization.