Lorenz demonstrated the concept of imprinting - this is where animals will attach to the first moving object or person they see directly after birth. Lorenz showed that imprinting occurred in a clutch of goose eggs, where half attached to and followed Lorenz after seeing him as the first moving person after birth. Imprinting/ the formation of an attachment must occur within the critical period of attachment development, which is usually the first 30 months of life, after which an attachment is not possible and the consequences of a failure to form an attachment are irreversible