Google's Project Aristotle found psychological safety to be the single most important factor distinguishing high-performing teams from average ones, more important than team composition, structure, or resources. Psychological safety means team members feel safe to take interpersonal risks including admitting mistakes, asking questions, and offering dissenting opinions without fear of punishment or humiliation. The article provides six specific practices for building psychological safety including framing work as learning problems, acknowledging fallibility, and modeling curiosity.