Freud also believed that the libido developed in individuals by changing its object, a process called "sublimation". He argued that humans are born "polymorphously perverse", meaning that any number of objects could be a source of pleasure. He further argued that, as humans develop, they become fixated on different and specific objects through their stages of development – first in the oral stage (exemplified by an infant's pleasure in nursing), then in the anal stage (exemplified by a toddler's pleasure in evacuating his or her bowels), then in the phallic stage.