从达尔文以来,许多学者观察到婴儿很早(大概在2—4月个)就可以对着成人的脸发出微笑。这种微笑,不是由生理舒适所引起,而是与成人交往所引起。近年来,不断有人观察到盲婴在同样的年龄,也开始对母亲的声音发出微笑。如果说盲婴不能通过视觉,还可通过触摸母亲的脸进行学习的话,那么德国马克斯·普兰克行为生理学研究报导的个案则排除了这种可能性:这个婴儿生来失明,而且没有前臂,但也出现了同样性质的微笑。这种微笑,显然不仅仅具有生理的功能,更主要 Since Darwin, many scholars have observed that babies smile at adult faces very early (about 2-4 months old). This smile, not caused by physiological comfort, but caused by the interaction with adults. In recent years, it has been observed that blind babies are at the same age and have begun to smile at their mothers’ voices. The case reported by the German Max Planck Institute for Behavioral Physiology ruled out the possibility that blind babies are blind and do not have forearms, if blind babies can not be visualized and can learn by touching their mother’s face. The same kind of smile appeared. This smile, obviously not only has the physiological function, more important