We are all curious about what people are thinking and what makes them tick. This urge to understand others helps us to adapt successfully to the world around us. Now, in Personal Intelligence, the renowned psychologist John D. Mayer reveals that we all possess a type of intelligence—a master guidance system—that allows us to understand the motives, traits, and plans that direct people’s personalities, including our own. Mayer, who co-developed the theory of emotional intelligence, argues that there exists a broader, guiding intelligence called “personal intelligence.” Drawing on classic case studies and cutting-edge research, and illustrating his points with examples from successful baseball players to talented portrait artists, he demonstrates that a diverse group of skills—previously regarded as unrelated—form a coherent mental ability that we use to evaluate ourselves and others. He shows how people high in personal intelligence (PI) solve problems that range from anticipating other people’s behaviour to motivating themselves over the long term. Describing these skills for the first time and providing readers with suggestions for ways to improve their own PI, Mayer puts forward an important message about personality and happiness.