The Modern Understanding of Cognitive Biases Has its Roots in Early Criticisms of the Rational Model of Human Behavior. Researchers Such as George Katona and Herbert Simon Introduced the Notion of Bounded Rationality, Highlighting how Cognitive Limitations Shape Judgment and Decision-Making. However, it Was the Dual-Process Theory, Formalized by Daniel Kahneman and Amos Tversky, that Definitively Established the Existence of Two Systems of Thought: One Fast, Intuitive, and Automatic (System 1), and another Slow, Deliberative, and Analytical (System 2). Building on these Foundations, Behavioral Economics Demonstrated that Human Decisions Follow Systematic Patterns Influenced by Mental Shortcuts, Giving Rise to Multiple Heuristics and Biases. This Chapter Reviews the Historical Development of these Ideas and Describes their Relevance in Clinical Settings. The most Important Heuristics Are Presented, along with their Evolutionary and Cognitive Foundations, and Practical Examples in the Medical Field. The Chapter Also Discusses how Cognitive Biases Can Negatively Impact Clinical Judgment and Therapeutic Decisions, Posing a Risk to Patient Safety. It Provides the Conceptual Framework for Understanding the Phenomena Analyzed in Subsequent Chapters