Language development and processing begins before birth. Evidence has shown that there is language development occurring antepartum. DeCasper and Spence performed a study in 1986 by having mothers read aloud during the last few weeks of pregnancy. When the infants were born, they were then tested. They were read aloud a story while sucking on a pacifier; the story was either the story read by the mother when the infant was in utero or a new story. The pacifier used was able to determine the rate of sucking that the infant was performing. When the story that the mother had read before was heard, the sucking of the pacifier was modified. This did not occur during the story that the infant had not heard before. The results for this experiment had shown that the infants were able to recognize what they had heard in utero, providing insight that language development had been occurring in the last six weeks of pregnancy.