Can nonhuman primate signals be arbitrarily meaningful like human words? An affective approach

Abstract

Cheney and Seyfarth's pioneering studies on vervet alarm calls reformed our knowledge about nonhuman's understanding of the world and their social relationships. Since then, it has been reported that some other primate species also have functionally referential alarm calls for aerial and terrestrial predators, but recent research indicates that these calls, or acoustic variants thereof, are also used in other contexts. Since the use of unspecific general alarm calls for terrestrial predators that are also used during aggressive interactions with conspecifics appears to be more common among primates, particularly in phylogenetically basal lemurs, these calls may present the ancestral form of primate alarm calling. In addition, intraspecific comparisons between populations that are exposed to different sets of predators also suggest that terrestrial predator alarm call usage and comprehension is more flexible than usage and comprehension of aerial alarm calls. Thus, primates can infer specific meaning from calls either based on their predator exposure history or by taking additional contextual information into account. The fact that they can even extract specific information from non-specific signals puts the utility of the original concept of functional reference into question.