We develop a formal semantic analysis of the alarm calls used by Campbell’s monkeys in the Tai forest and on Tiwai island —two sites that differ in the main predators that the monkeys are exposed to. Building on data discussed in Ouattara et al. :e7808, 2009a; PNAS 106: 22026–22031, 2009b and Arnold et al., we argue that on both sites alarm calls include the roots krak and hok, which can optionally be affixed with -oo, a kind of attenuating suffix; in (...) addition, sentences can start with boom boom, which indicates that the context is not one of predation. In line with Arnold et al., we show that the meaning of the roots is not quite the same in Tai and on Tiwai: krak often functions as a leopard alarm call in Tai, but as a general alarm call on Tiwai. We develop models based on a compositional semantics in which concatenation is interpreted as conjunction, roots have lexical meanings, -oo is an attenuating suffix, and an all-purpose alarm parameter is raised with each individual call. The first model accounts for the difference between Tai and Tiwai by way of different lexical entries for krak. The second model gives the same underspecified entry to krak in both locations, but it makes use of a competition mechanism akin to scalar implicatures. In Tai, strengthening yields a meaning equivalent to non-aerial dangerous predator and turns out to single out leopards. On Tiwai, strengthening yields a nearly contradictory meaning due to the absence of ground predators, and only the unstrengthened meaning is used. (shrink)

Compared to other animals, humans appear to have a special motivation to share experiences and mental states with others (Clark, 2006; Grice, 1975), which enables them to enter a condition of ‘we’ or shared intentionality (Tomasello & Carpenter, 2005). Shared intentionality has been suggested to be an evolutionary response to unique problems faced in complex joint action coordination (Levinson, 2006; Tomasello, Carpenter, Call, Behne, & Moll, 2005) and to be unique to humans (Tomasello, 2014). The theoretical and empirical bases for (...) this claim, however, present several issues and inconsistencies. Here, we suggest that shared intentionality can be approached as an interactional achievement, and that by studying how our closest relatives, the great apes, coordinate joint action with conspecifics, we might demonstrate some correlate abilities of shared intentionality, such as the appreciation of joint commitment. We provide seven examples from bonobo joint activities to illustrate our framework. (shrink)

Language’s intentional nature has been highlighted as a crucial feature distinguishing it from other communication systems. Specifically, language is often thought to depend on highly structured intentional action and mutual mindreading by a communicator and recipient. Whilst similar abilities in animals can shed light on the evolution of intentionality, they remain challenging to detect unambiguously. We revisit animal intentional communication and suggest that progress in identifying analogous capacities has been complicated by (i) the assumption that intentional (that is, voluntary) production (...) of communicative acts requires mental-state attribution, and (ii) variation in approaches investigating communication across sensory modalities. To move forward, we argue that a framework fusing research across modalities and species is required. We structure intentional communication into a series of requirements, each of which can be operationalised, investigated empirically, and must be met for purposive, intentionally communicative acts to be demonstrated. Our unified approach helps elucidate the distribution of animal intentional communication and subsequently serves to clarify what is meant by attributions of intentional communication in animals and humans. (shrink)

Compared to other animals, humans appear to have a special motivation to share experiences and mental states with others (Clark, 2006; Grice, 1975), which enables them to enter a condition of ‘we’ or shared intentionality (Tomasello & Carpenter, 2005). Shared intentionality has been suggested to be an evolutionary response to unique problems faced in complex joint action coordination (Levinson, 2006; Tomasello, Carpenter, Call, Behne, & Moll, 2005) and to be unique to humans (Tomasello, 2014). The theoretical and empirical bases for (...) this claim, however, present several issues and inconsistencies. Here, we suggest that shared intentionality can be approached as an interactional achievement, and that by studying how our closest relatives, the great apes, coordinate joint action with conspecifics, we might demonstrate some correlate abilities of shared intentionality, such as the appreciation of joint commitment. We provide seven examples from bonobo joint activities to illustrate our framework. (shrink)

How does intentional communication evolve? Comparative studies can shed light on the evolutionary history of this relevant feature of human language and its distribution before modern humans. The current animal literature on intentional signaling consists mostly of ape gestural studies with evidence of subjects persisting and elaborating with sometimes arbitrary signals toward a desired outcome. Although vocalizations can also have such imperative qualities, they are typically produced in a functionally fixed manner, as if evolved for a specific purpose. Yet, intentionality (...) can sometimes transpire even in functionally fixed calls, for example, if production is adapted to audience composition. In this study, we carried out field experiments to test whether free-ranging sooty mangabeys adjusted snake alarm call production to their audiences. We found a positive relation between alarm call production and naïve individuals arriving, suggesting that callers attempted to influence their behaviors relative to the snake. Subjects called more with smaller audiences, if they had not heard other calls before, and if socially important individuals were in the area. We concluded that sooty mangabeys alarm call production can be explained as an active attempt to refer to an external event, rather than a mere readout of an internal state. (shrink)

The two main theories of food-associated calls in animals propose functions either in cooperative recruitment or competitive spacing. However, not all social animals produce food calls and it is largely unclear under what circumstances this call type evolves. Sooty mangabeys do not have food calls, but they frequently produce grunts during foraging, their most common vocalisation. We found that grunt rates were significantly higher when subjects were foraging in the group’s periphery and with small audiences, in line with the cooperative (...) recruitment hypothesis. In a subsequent field experiment we presented highly desired food items and found that discovering individuals called, unless harassed by competitors, but that the calls never attracted others, confirming that the grunts do not convey any information referential to food. Our data thus suggest that the evolution of cooperative food calling is a two-step process, starting with increased motivation to vocalise in the feeding context, followed by the evolution of acoustic variants derived from context-general contact calls. This evolutionary transition may only occur in species that feed on clumped, high-quality resources where social feeding is competitive, a condition not met in sooty mangabeys. (shrink)