Suckling motions were investigated by recording the oral motions of normal infants suckling their mother's milk using ultrasonic tomographic images from below the mandibular foramen. The suckling motion was revealed to be a back and forth waving motion of the whole tongue, including the root of the tongue beginning from the tongue tip and extending to the epiglottis, and a peristalsis-like motion which fixes and presses the nipple and transports the emerging milk.
The oral motion around the tongue was also recorded with a small video camera built into a suction bottle, and the suckling motion was simultaneously using an instruments developed to measure the suckling pressure. The suckling motion of the tongue was revealed to be a peristalsis-like motion in which the tongue closely surrounds the nipple and the center of the tongue presses the palate first with the anterior part of the tongue and subsequently with the posterior part of the tongue. Up to the age of three months, the suckling pressure waveforms are regular, and suckling occurs as frequently as 80-90 per minute with a constant suckling pressure.