The checklist is an effective tool for reducing human error and improving outcomes. Checklists were developed after aviation accidents to improve plane safety, and reduced medical errors when used in intensive care units. Checklists work because the human mind is prone to shortcuts and emotions that can lead to mistakes. Learning from mistakes through checklists is more effective than experiencing mistakes directly. Great investors like Warren Buffett continually learn from their own mistakes and those of others to improve their investment checklists over time.