Studies of parent-child attachment, parental satisfaction and infant crying point to babywearing as a satisfactory arrangement for both parents and baby. Baby carriers and slings help increase the number of hours a day an infant is held, and proponents believe that the more a baby is held, the less the baby cries. However, this experience is not universal; for example, the indigenous Munduruku people of Brazil use baby slings to carry their babies all day. The babies are allowed to nurse freely, and are passed from one woman or girl to another to be carried throughout the day. Yet, the Munduruku babies cry very frequently despite being carried all day.