Starting around 8 to 10 months, children begin to look at the facial expressions of others to help themselves decide what to do. In a way, children become able to “read” the emotional meaning of another person’s facial expressions. This is called social referencing–looking for emotional clues about a situation in the faces of other people. For example, if a child sees a fearful expression on his mother’s face as he reaches to touch something, he will be less likely to touch it. If the child sees an approving or excited look, he will be more likely to go ahead and touch the object.
Sorce, J. F., Emde, R. N., Campos, J., & Klinnert, M. (1985). Maternal emotional signaling: Its effect on the visual cliff behavior of 1-year-olds. Developmental Psychology, 21(1), 195
Walden, T. & Ogan, T. (1988). The development of social referencing. Child Development, 59, 1230