Ackermann et al. mention the “acquisition of species-atypical sounds” in apes without any discussion. In our commentary, we demonstrate that these atypical sounds in chimpanzees not only include laryngeal sounds, but also have a major significance regarding the origins of language, if we consider looking at their context of use, their social properties, their relations with gestures, their lateralization, and their neurofunctional correlates as well.

Henrich et al. convincingly caution against the overgeneralization of findings from particular human populations, but fail to apply their own compelling reasoning to our nearest living relatives, the great apes. Here we argue that rearing history is every bit as important for understanding cognition in other species as it is in humans.

Corballis suggests that apes lack voluntary control over their vocal production. However, recent evidence implicates voluntary control of vocalizations in apes, which suggests that intentional control of vocal communication predates the hominid-pongid split. Furthermore, the ease with which apes in captivity manipulate the visual attention of observers implies a common cognitive basis for joint attention in humans and apes.

Comparative and developmental psychology are engaged in a search for the evolutionary and developmental origins of the perceptions of “intentions” and “desires,” and of epistemic states such as “ignorance” and “false belief.” Shanker & King (S&K) remind us that these are merely words to describe public events: All organisms that can discriminate states of “knowledge” in others have learned to do this through observation of publicly available information.

That organisms have a concept “see” does not necessarily entail that they attribute knowledge to others or predict others' behaviors on the basis of inferred mental states. An alternative experimental protocol is proposed in which accurate prediction of the location of an experimenters' impending appearance is contingent upon subjects' attribution of knowledge to the experimenter.