Cognitive illusions are errors in thinking that occur when our brain misinterprets information. These illusions can lead to false beliefs or judgments, often influenced by biases, emotions, or context. For example, the Müller-Lyer illusion demonstrates how our perception of line length can be distorted by the surrounding arrows. These illusions highlight the limitations of human cognition and how our mental processes can be tricked. Understanding cognitive illusions is important in fields like psychology and behavioral economics, as they can affect decision-making and problem-solving in everyday life.