Apes communicate about absent and displaced objects: Methodology matters (original) (raw)
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Apes communicate about absent and displaced objects: Methodology matters (2014).
Displaced reference is the ability to refer to an item that has been moved (displaced) in space and/or time, and has been called one of the true hallmarks of referential communication. Several studies suggest that nonhuman primates have this capability, but a recent experiment concluded that in a specific situation (absent entities), human infants display displaced reference but chimpanzees do not. Here, we show that chimpanzees and bonobos of diverse rearing histories are capable of displaced reference to absent and displaced objects. It is likely that some of the conflicting findings from animal cognition studies are due to relatively minor methodological differences, but are compounded by interpretation errors. Comparative studies are of great importance in elucidating the evolution of human cognition; however, greater care must be taken with methodology and interpretation for these studies to accurately reflect species differences.
Prelinguistic Infants, but Not Chimpanzees, Communicate About Absent Entities
Psychological Science, 2009
One of the defining features of human language is displacement, the ability to make reference to absent entities. Here we show that prelinguistic, 12-month-old infants already can use a nonverbal pointing gesture to make reference to absent entities. We also show that chimpanzees—who can point for things they want humans to give them—do not point to refer to absent entities in the same way. These results demonstrate that the ability to communicate about absent but mutually known entities depends not on language, but rather on deeper social-cognitive skills that make acts of linguistic reference possible in the first place. These nonlinguistic skills for displaced reference emerged apparently only after humans' divergence from great apes some 6 million years ago.
Is displacement possible without language? Evidence from preverbal infants and chimpanzees
Philosophical Psychology, 2013
ABSTRACT Is displacement possible without language? This question was addressed in a recent work by Liszkowski and colleagues (Liszkowski, Schafer, Carpenter, & Tomasello, 2009). The authors carried out an experiment to demonstrate that 12-month-old prelinguistic infants can communicate about absent entities by using pointing gestures, while chimpanzees cannot. The main hypothesis of their study is that displacement does not depend on language but is, however, exclusively human and instead depends on species-specific social-cognitive human skills. Against this hypothesis, we will argue that a symbolic representation is needed to intentionally communicate absence and that this symbolic representation is tied to language. Moreover, data on the expression of displacement in home-sign systems will be taken into consideration. In light of this data, and in opposition to Liszkowski et al.'s (2009) claim, this paper will argue that displacement gestures are not foundational to language. Instead, they predate and predict the expression of complex forms of negation because they are specifically foundational to them.
The higher the farther: distance-specific referential gestures in chimpanzees ( Pan troglodytes )
Biology Letters, 2017
Referential signals, such as manual pointing or deictic words, allow individuals to efficiently locate a specific entity in the environment, using distance-specific linguistic and/or gestural units. To explore the evolutionary prerequisites of such deictic ability, the present study investigates the ability of chimpanzees to adjust their communicative signals to the distance of a referent. A food-request paradigm in which the chimpanzees had to request a close or distant piece of food on a table in the presence/absence of an experimenter was employed. Our main finding concerns the chimpanzees adjusting their requesting behaviours to the distance of the food such that higher manual gestures and larger mouth openings were used to request the distant piece of food. To the best of our knowledge, this is the first study to demonstrate that chimpanzees are able to use distance-specific gestures.
The concept of functional reference has been used to isolate potentially referential vocal signals in animal communication. However, its relatedness to the phenomenon of reference in human language has recently been brought into question. While some researchers have suggested abandoning the concept of functional reference altogether, others advocate a revision of its definition to include contextual cues that play a role in signal production and perception. Empirical and theoretical work on functional reference has also put much emphasis on how the receiver understands the referential signal. However, reference, as defined in the linguistic literature, is an action of the producer, and therefore any definition describing reference in non-human animals must also focus on the producer. To successfully determine whether a signal is used to refer, we suggest an approach from the field of pragmatics, taking a closer look at specific situations of signal production, specifically at the factors that influence the production of a signal by an individual. We define the concept of signaller's reference to identify intentional acts of reference produced by a signaller independently of the communicative modality; and illustrate it with a case study of the hoo vocalisations produced by wild chimpanzees during travel. This novel framework introduces an intentional approach to referentiality. It may therefore permit a closer comparison of human and non-human animal referential behaviour and underlying cognitive processes, allowing us to identify what may have emerged solely in the human lineage.
Becoming human: human infants link language and cognition, but what about the other great apes?
Philosophical Transactions of the Royal Society B: Biological Sciences
Human language has no parallel elsewhere in the animal kingdom. It is unique not only for its structural complexity but also for its inextricable interface with core cognitive capacities such as object representation, object categorization and abstract rule learning. Here, we (i) review recent evidence documenting how (and how early) language interacts with these core cognitive capacities in the mind of the human infant, and (ii) consider whether this link exists in non-human great apes—our closest genealogical cousins. Research with human infants demonstrates that well before they begin to speak, infants have already forged a link between language and core cognitive capacities. Evident by just three months of age, this language–cognition link unfolds in a rich developmental cascade, with each advance providing the foundation for subsequent, more precise and more powerful links. This link supports our species' capacity to represent and convey abstract concepts and to communicate...
Functionally Referential Communication in a Chimpanzee
Current Biology, 2005
The evolutionary origins of the use of speech signals to refer to events or objects in the world have remained obscure. Although functionally referential calls have been described in some monkey species [1, 2], studies with our closest living relatives, the great apes, have not generated comparable findings. These negative results have been taken to suggest that ape vocalizations are not the product of their otherwise sophisticated mentality and that ape gestural communication is more informative for theories of language evolution [3, 4]. We tested whether chimpanzee rough grunts, which are produced during feeding contexts [5-8], functioned as referential signals. Individuals produced acoustically distinct types of "rough grunts" when encountering different foods. In a naturalistic playback experiment, a focal subject was able to use the information conveyed by these calls produced by several group mates to guide his search for food, demonstrating that the different grunt types were meaningful to him. This study provides experimental evidence that our closest living relatives can produce and understand functionally referential calls as part of their natural communication. We suggest that these findings give support to the vocal rather than gestural theories of language evolution.