OUP UNCORRECTED PROOF – FIRST-PROOF, 09/26/11, NEWGEN CHAPTER Socio-Cognitive Specializations in Nonhuman Primates: Evidence from 1 0 Gestural Communication Erica Cartmill and Dario Maestripieri Abstract This chapter reviews primate cognitive abilities in physical, social, and communicative realms and asks (1) whether primates exhibit abilities that diff er from those of other animals, and (2) what selective pressures primates face that may have led to the emergence of specifi c cognitive abilities. The authors focus on communication as the most likely realm for primate cognitive specialization and on the gestural communication of great apes as the modality in which primates exhibit the most advanced cognitive abilities. Findings from studies of natural communication systems of both wild and captive primates as well as studies involving communication with human experimenters are presented and discussed. Apes demonstrate fl exibility, learning, and sensitivity to social cues in their gestural communication, but further studies are needed to determine how gestures are acquired and how they are perceived. Studies of comparative development of gestural communication and social cognition have the greatest potential to reveal the cognitive abilities used during gesturing, and they will help to determine whether those abilities are truly specializations for communication. Key Words: Great ape, communication, gesture, social cognition, development Introduction fl exibly, with the individual organism making deci- Primate Cognitive Adaptations sions among possible courses of action based on an Th e past 30 years have witnessed an explosion of assessment of the current situation in relation to its research on all aspects of primate cognition. Much current goal; and (2) involve some kind of men- of this new research has been fueled by the cogni- tal representation that goes beyond the informa- tive revolution in psychology and ethology, which tion given to direct perception” (Tomasello & Call, prompted a shift from the study of learned behav- 1997, p. 8). ior to the study of mental representations of the Flexibility is central to cognition, because with- self and of the physical and social environment. A out some agency in choosing to perform an action further impetus is the framing of cognitive inves- or having a range of possible actions to confront tigations within ecology and evolutionary biology. a problem or achieve a goal, an animal’s response Th is framing has led to a new understanding of the would most likely be an automatic response to a ecological signifi cance and evolutionary origins of reoccurring environmental situation. Some complex cognitive adaptations. behaviors may seem like cognitive adaptations, but Primate cognitive adaptations can be thought of if the behaviors are infl exible responses to the envi- as complex “behavioral adaptations in which per- ronment, then they are considered behavioral adap- ceptual and behavioral processes (1) are organized tations, not cognitive ones. Th e idea that an animal 1 110_Vonk_Ch10.indd0_Vonk_Ch10.indd 1 99/26/2011/26/2011 111:47:051:47:05 PPMM OUP UNCORRECTED PROOF – FIRST-PROOF, 09/26/11, NEWGEN has some agency over what variables of the environ- As in many areas of cognitive research, there is a ment it attends to and how it acts in response to wide gap between the abilities apes demonstrate in those variables is at the foundation of attributing experimental settings and those they employ dur- cognitive processes to animals, and fl exibility lies at ing conspecifi c communication in wild or captive the heart of agency. groups. We compare results from studies of wild Mental representation of some type is also a key and captive conspecifi c gesture, artifi cial-language element in cognition. Complex, human-like repre- studies, and experiments in which captive apes sentation based on images or symbols is not required communicate with humans but by using their natu- or implied. Rather, this representation involves the ral communication systems. Taken together, these ability to make decisions based on perceptions of results demonstrate that the cognitive skills apes the external world by extracting relevant environ- use during gestural communication should be con- mental features, holding information in working or sidered cognitive adaptations, though many ques- long-term memory, comparing several things, cate- tions remain. Th e captive studies demonstrate the gorizing things, or recognizing similarities between importance of the developmental period in estab- the immediate environment and a previously solved lishing and encouraging the acquisition and use of problem. Animals that appear to display “intelli- both cognitive and communicative abilities. Com- gent” choices, generalized learning, or insight are all parative studies focusing on the role of ontogeny in employing mental representations that allow them the development of cognitive abilities and on the to learn or make decisions outside the context of tri- interaction between cognitive and communicative al-and-error learning (see Tomasello & Call, 1997). abilities during ontogeny hold the greatest poten- Cognitive adaptations and their underlying neu- tial for providing insight into whether the cognitive ral substrates evolve by natural selection in response abilities used in gestural communication evolved as to recurrent problems posed by the physical, ecolog- specializations for communication. ical, or social environment, but they are selected at the cognitive rather than the behavioral level. Th ey Physical Cognition involve the ability to make decisions about what to Th e study of primate cognitive adaptations has do in a particular situation based on the perception involved many aspects of physical and social cogni- or understanding of contextual variables rather than tion. Primate research in the domain of physical cog- precise behavioral responses to external stimuli. nition has addressed how monkeys and apes acquire Cognitive adaptations may be general abilities (e.g., information about the physical space in which they the ability to inhibit a behavior), or they may per- live and the inanimate objects in it, how this infor- tain to specifi c contexts or environmental problems mation is mentally represented and processed, and (e.g., the ability to make probing tools). how it is retrieved and used to make decisions. Free- In this chapter, we ask fi rst whether the primate ranging primates form spatial maps that represent order as a whole exhibits cognitive adaptations that the environment in which they live and use them to diff er from those of other animals, and second we make travel decisions as they search for food within ask what pressures primates face that may have led their home range (for a review see Janson & Byrne, to the emergence of specifi c cognitive abilities. In 2007). In the laboratory, primates exhibit knowledge the introduction, we discuss primates’ abilities in of movements of objects through space and under- the realms of physical cognition, social cognition, standing of object permanence, that is, the notion and communication. We focus on communication, that objects continue to exist and maintain their and on gestural communication in particular, as an features and properties if they have been moved or area in which there is great evidence for both fl ex- hidden from view (Barth & Call, 2006; Call, 2001). ibility and mental representation. In an attempt to For example, primates search for hidden objects, determine whether primates that are phylogeneti- and some can solve tasks that require the mental cally closest to humans show evidence of cognitive rotation of objects (Call, 2000; Vauclair, Fagot, & specializations similar to those of the human spe- Hopkins, 1993). Th ough primates are profi cient cies, we discuss facial expressions and body postures at these tasks, there is no evidence that primates in both apes and monkeys. We then concentrate have greater understanding of space and objects on the manual gestures of great apes as the type relative to other mammals, nor is there evidence of communication that demonstrates the greatest of signifi cant diff erences among primate species fl exibility. (e.g., between monkeys and apes). socio-cognitive specializations in nonhuman primates 110_Vonk_Ch10.indd0_Vonk_Ch10.indd 2 99/26/2011/26/2011 111:47:061:47:06 PPMM OUP UNCORRECTED PROOF – FIRST-PROOF, 09/26/11, NEWGEN Other research in the domain of physical cog- Social Cognition nition has involved object manipulation tasks, in Social cognition has been a topic of great interest which objects are used in relation to other objects, in primate research over the past 50 years, and there and which require an understanding of causality is now a growing focus on social cognition research (e.g., the relation between the use of the tool and in a wide range of nonprimate species. Th ese stud- the goal to be accomplished with it). Many spe- ies are driven in part by our desire to understand cies of primates, and especially capuchin monkeys the evolutionary pressures underlying the develop- and the great apes, are profi cient tool users and also ment of human social cognition, including the abil- show some evidence of understanding of causality ity to be aware of the self and others; to empathize, (although see Povinelli, 2000). However, primates’ cooperate, inform, create, and share symbols; and to tool using skills have been matched or even sur- hold collective beliefs. Many complex human abil- passed by the tool