The two primary channels of communication in primate species are the face and the voice. Normally, facial gestures and accompanying vocalizations provide highly redundant information because they are
produced in the same modality (i.e., the face and the voice). However, in some species, the face and the voice are not always in synchrony. For example, in humans, the face and the voice are not always in synchrony, and the face and the voice are not always in synchrony