The term “Neuroception” describes how neural circuits distinguish whether situations or people are safe, dangerous, or life threatening. Neuroception explains why a baby coos at a caregiver but cries at a stranger, or why a toddler enjoys a parent’s embrace but views a hug from a stranger as an assault. The author explains the Polyvagal Theory, which posits that mammals–especially primates–have evolved brain structures that regulate both social and defensive behaviors. The Polyvagal Theory describes three developmental stages of a mammal’s autonomic nervous system: immobilization, mobilization, and social communication or social engagement. A neuroception of safety is necessary before social engagement behaviors can occur. Infants, young children, and adults need appropriate social engagement strategies in order to form positive attachments and social bonds. Faulty neuroception might lie at the root of several psychiatric disorders, including autism, schizophrenia, anxiety disorders, depression, and Reactive Attachment Disorder.