The higher the farther: distance-specific referential gestures in chimpanzees (Pan troglodytes)

A conceptual framework for the study of demonstrative reference

Language allows us to efficiently communicate about the things in the world around us. Seemingly simple words like this and that are a cornerstone of our capability to refer, as they contribute to guiding the attention of our addressee to the specific entity we are talking about. Such demonstratives are acquired early in life, ubiquitous in everyday talk, often closely tied to our gestural communicative abilities, and present in all spoken languages of the world. Based on a review of recent experimental work, here we introduce a new conceptual framework of demonstrative reference. In the context of this framework, we argue that several physical, psychological, and referent-intrinsic factors dynamically interact to influence whether a speaker will use one demonstrative form (e.g., this) or another (e.g., that) in a given setting. However, the relative influence of these factors themselves is argued to be a function of the cultural language setting at hand, the theory-of-mind capacities of the speaker, and the affordances of the specific context in which the speech event takes place. It is demonstrated that the framework has the potential to reconcile findings in the literature that previously seemed irreconcilable. We show that the framework may to a large extent generalize to instances of endophoric reference (e.g., anaphora) and speculate that it may also describe the specific form and kinematics a speaker's pointing gesture takes. Testable predictions and novel research questions derived from the framework are presented and discussed.

Effects of Scale on Multimodal Deixis: Evidence From Quiahije Chatino

As humans interact in the world, they often orient one another's attention to objects through the use of spoken demonstrative expressions and head and/or hand movements to point to the objects. Although indicating behaviors have frequently been studied in lab settings, we know surprisingly little about how demonstratives and pointing are used to coordinate attention in large-scale space and in natural contexts. This study investigates how speakers of Quiahije Chatino, an indigenous language of Mexico, use demonstratives and pointing to give directions to named places in large-scale space across multiple scales (local activity, district, state). The results show that the use and coordination of demonstratives and pointing change as the scale of search space for the target grows. At larger scales, demonstratives and pointing are more likely to occur together, and the two signals appear to manage different aspects of the search for the target: demonstratives orient attention primarily to the gesturing body, while pointing provides cues for narrowing the search space. These findings underscore the distinct contributions of speech and gesture to the linguistic composite, while illustrating the dynamic nature of their interplay.

Abstracts in Spanish and Quiahije Chatino are provided as appendices.

Se incluyen como apéndices resúmenes en español y en el chatino de San Juan Quiahije. Son^G ktyi^C re^C in^H, ngyaq^C ska^E ktyi^C no^E nda^H son^B na^F nga^J no^I ngyaq^C lo^E ktyi^C re^C, ngyaq^C ran^F chaq^E xlya^K qo^E chaq^F jnya^J no^A ndywiq^A renq^A Kchin^A Kyqya^C.

Context-sensitive adjustment of pointing in great apes

Great apes are able to request objects from humans by pointing. It is unclear, however, whether this is an associated response to a certain set of cues (e.g. the presence and attention of a human addressee) or a communicative signal which can be adjusted to relevant aspects of the spatial and social context. In three experiments, we tested captive great apes’ flexible use of pointing gestures. We manipulated the communicative context so that the default pointing response of apes would have indicated an undesired object, either due to 1) the spatial arrangements of the target objects, 2) the perspective of the addressee or 3) the knowledge of the addressee about the target objects’ location. The results of the three experiments indicate that great apes can successfully adjust their pointing to the spatial configuration of the referent environment such as distance and location of food. However, we found no evidence that they take the perspective or the knowledge of the addressee into account when doing so. This implies that pointing in great apes is a context-sensitive, but maybe less versatile, communicative signal compared to human pointing.

Complex Sociality of Wild Chimpanzees Can Emerge from Laterality of Manual Gestures

Humans are strongly lateralized for manual gestures at both individual and population levels. In contrast, the laterality bias in primates is less strong, leading some to suggest that lateralization evolved after the Pan and Homo lineages diverged. However, laterality in humans is also context-dependent, suggesting that observed differences in lateralization between primates and humans may be related to external factors such as the complexity of the social environment. Here we address this question in wild chimpanzees and examine the extent to which the laterality of manual gestures is associated with social complexity. Right-handed gestures were more strongly associated with goal-directed communication such as repair through elaboration in response to communication failure than left-handed gestures. Right-handed gestures occurred in evolutionarily urgent contexts such as in interactions with central individuals in the network, including grooming reciprocity and mating, whereas left-handed gestures occurred in less-urgent contexts, such as travel and play. Right-handed gestures occurred in smaller parties and in the absence of social competition relative to left-handed gestures. Right-handed gestures increased the rate of activities indicating high physiological arousal in the recipient, whereas left-handed gestures reduced it. This shows that right- and left-handed gestures differ in cognitive and social complexity, with right-handed gestures facilitating more complex interactions in simpler social settings, whereas left-handed gestures facilitate more rewarding interactions in complex social settings. Differences in laterality between other primates and humans are likely to be driven by differences in the complexity of both the cognitive skills underpinning social interactions and the social environment.