Infants have fully developed their locomotive abilities within three to four months. When an infant is seven months old, its mother discourages suckling; full weaning happens by its 18th month. In some populations, male infants tend to play in larger groups more often than females. However, female infants have more social interaction than their male counterparts. Males prefer to associate with other males around the same age when they are two years old. Female infants will associate with individuals of all ages and sexes.