Neonatal microrhythms and their intrapersonal synchrony between crying vocalization and arm movement were preliminarily researched using a newly developed quantitative analyzing methodology aimed at developing a neurological assessment index. Subjects were twelve 1- to 17-day-old full-term appropriate-for-date neonates. Significant synchronous as well as lagged relationships between crying vocalization and arm movement were revealed. It was found that at the beginning of the cry, movement preceded the cry, while there was no dominant action seen at the end of the cry. It is suggested that this methodology is important as a possible indicator of the integrity of early neural mechanisms.