The present invention relates to a system and method for increasing the cognitive function in a fetus. The system transmits a pattern of sonic variations to the fetus. The pattern of sonic variations is formed of a plurality of sequences of tones in which each sequence is repeated at a predetermined tempo. Each sequence of tones is selected to be transmitted to the fetus at a predetermined time during the term of the pregnancy. Preferably, each subsequent sequence of tones is selected to be repeated at increasing tempo during the term of the pregnancy, thereby providing a progressive pattern of sonic variations. A similar system and method can be used for improving the cognitive function of a premature baby. In addition, the present invention relates to a system and method for altering the cognitive function in a postnatal human by transmitting aurally or through bone conduction a progressive pattern of sonic variations or a regressive pattern of sonic variations to the wearer of the system.