Can leadership be measured in blood? The Shibboleth Effect asks what happens when leaders are exposed not to strategies or tools, but to a powerful experience of art. The book explores how confronting vulnerability, tragedy and moral ambiguity through poetry and music reshapes responsibility and how power is understood and exercised. Building on insights from neuroscience, philosophy and psychology, Julia Romanowska reveals how the shock and beauty of art can unsettle leaders' judgment and sense of self. At the centre of the book is the Shibboleth leadership programme, evaluated in a randomised study showing measurable changes in leaders, with effects extending to the stress hormone levels of their employees. Uniting aesthetics, emotion and ethics, the book argues for a form of leadership grounded in exposure rather than control and in responsibility rather than technique. Romanowska terms this integration aestemethics and challenges reductive models of leadership training, opening another horizon for leadership. Leadership, Art, and Responsibility will interest scholars and students of leadership, management, organisational health psychology, philosophy and cultural studies, as well as practitioners seeking ethically grounded forms of organisational life and workplace wellbeing. It insists on responsibility when the dignity of human life is at stake - and consequences cannot be undone.