"Cognitive Nemesis" explores the intricate relationships among reinforcement loops, confirmation bias, echo chambers, cognitive dissonance, metacognition, and the Dunning-Kruger effect within the context of modern digital media. It synthesizes these established cognitive and behavioral concepts and integrates an array of scientific literature to provide original insights into how digital environments and their dynamics impact human cognition and behavior. These insights result from extensive research at the Zentrum für Medienpsychologie und Verhaltensforschung (ZeMV), and serve as an exploratory analysis offering new perspectives on the impact of technology on cognition and resulting behavior, on an individual and societal scale. Solidified through numerous real-world applications and case studies, the implications of this book can enhance the understanding of psychological explanations for phenomena, that are observed in a digitally immersed society.