In human infancy, 2 criteria for intentional communication are (a) persistence in and (b) elaboration of communication when initial attempts to communicate fail. Twenty-nine chimpanzees (Pan troglodytes) were presented with both desirable (a banana) and undesirable food (commercial primate chow). Three conditions were administered: (a) the banana was delivered (successful communication), (b) half of the banana was delivered (partially successful communication), and (c) the chow was delivered (failed communication). The chimpanzees exhibited persistence in and elaboration of their communication in every condition except when the banana was delivered. Thus, their communication was about a specific item, demonstrating that both intentionality and nonverbal reference are capacities shared by humans with our nearest living relatives, the great apes.A significant milestone in human development is the transition to intentional communication, traditionally held to begin at about 10 to 12 months of age (e.g., Butterworth, 2001;Lock, 2001). One of the most replicated observations from studies of human communicative development is that sometime around the end of the 1st year of life, babies begin to point to distant objects (Franco & Butterworth, 1996;Leung & Rheingold, 1981). Until recently, pointing was held to be a uniquely human capacity (Donald, 1991;Povinelli & Davis, 1994;Povinelli, Bering, & Giambrone, 2003), but anecdotal reports of pointing by our nearest living relatives, the chimpanzees, have existed in the scientific literature for almost 90 years (e.g., Furness, 1916; reviewed by Leavens & Hopkins, 1999). More recently, experimental investigations have demonstrated that chimpanzees in captivity frequently point to distal objects in the absence of any explicit training (e.g., Krause & Fouts, 1997;Leavens & Hopkins, 1998Leavens, Hopkins, & Bard, 1996;Leavens, Hopkins, & Thomas, 2004).We characterize pointing by apes as a referential activity (Hopkins & Leavens, 1998;Leavens & Hopkins, 1998;Leavens et al., 1996;, meaning simply that apes and humans who use their outstretched arms and fingers to indicate distant objects or events are referring to specific entities. Because we differ in this use of the term reference from the more typical usages in developmental psycholinguistics, a brief explanatory digression is warranted. In symbolic reference, the term refers to the arbitrary nature of the relationship between an entity and the label used to signify that entity. Thus, the word big is not, in fact, bigger than the word little. For most linguists, the term reference is synonymous with symbolic reference; however, developmental psychologists interested in human communicative development have identified pointing as a class of behavior that functionally constitutes Correspondence concerning this article should be sent to David A. Leavens, Psychology Department, School of Life Sciences, University of Sussex, Falmer, East Sussex BN1 9QH. Electronic mail may be sent to davidl@sussex.ac.uk.

The spontaneous index finger and other referential pointing in 3 adult, laboratory chimpanzees (Pan troglodytes) who have not received language training is reported. Of 256 total observed points, 254 were emitted in the presence of a human to objects in the environment; therefore, the points were communicative. Indicators of intentional communication used by the subjects included attention-getting behaviors, gaze alternation, and persistence until reward. Thus, pointing by these chimpanzees was intentionally communicative. These data imply that perspective-taking and referential communication are generalized hominoid traits, given appropriate eliciting contexts. Index finger pointing was more frequent with the subjects' dominant hands. This study refutes claims that indexical or referential pointing is species-unique to humans or dependent on linguistic competence or explicit training.This study was initiated when a chimpanzee began to regularly point to accidentally dropped food items outside his home cage and beyond his reach in the presence of an experimenter. We sought to determine if this pointing behavior could be defined as intentional communication, and not simple reaching, by comparing the pointing behavior of this subject and two cagemates with pointing and intentional communication in human infants.The production and comprehension of referential pointing in preverbal humans have been increasingly studied in recent decades with respect to their significance for the attribution of intentionality in preverbal children

This study describes the use of referential gestures with concomitant gaze orienting behavior to both distal food objects and communicative interactants by 115 chimpanzees, ranging from 3 to 56 years of age. Gaze alternation between a banana and an experimenter was significantly associated with vocal and gestural communication. Pointing was the most common gesture elicited; 47 subjects pointed with the whole hand, whereas 6 subjects pointed with index fingers. Thus, communicative pointing is commonly used by laboratory chimpanzees, without explicit training to point, language training, or home rearing. Juveniles exhibited striking decrements in their propensity to communicate with adult male experimenters compared with older chimpanzees. Significantly fewer mother-reared chimpanzees exhibited gaze alternation compared with nursery-reared chimpanzees.Pointing in humans becomes an intentionally communicative gesture at about 12 months of age (e.g., Bates, Camaioni, & Volterra, 1975;Blake, O'Rourke, & Borzellino, 1994;Bruner, 1975;Franco & Butterworth, 1996;Leung & Rheingold, 1981). Intentional, mature use of pointing is defined as pointing with reference to the attentional status of an observer; this is measured by the gaze behavior of pointing individuals. One measure of gaze behavior used to identify intentional communication in humans is gaze alternation, in which the signaler alternates his or her gaze between a distal object or location and the face of the recipient of a gesture (e.g., Harding & Golinkoff, 1979;Tomasello, 1995).Recent work examining intentional communication and social referencing in apes in a variety of free-ranging and laboratory settings also relies on measures of visual orienting behavior to establish that communication by these close relatives of humans is "about" specific objects in the environment (e.g., Bard, 1990Bard, , 1992Gómez, Sarriá, & Tamarit, 1993;Leavens, Hopkins, & Bard, 1996;Miles, 1990;Russell, Bard, & Adamson, 1997;Tomasello, George, Kruger, Farrar, & Evans, 1985;de Waal, 1982). For example, Tomasello et al. (1985) reported that only the 2 oldest of their sample of 5 juvenile chimpanzees exhibited gaze alternation while gesturing. More recently, Russell et al. (1997), in their study of social referencing, found that each of 17 infant and juvenile chimpanzees exhibited referential glancing (gaze alternation) between a novel object and the faces of their primary caregivers. Russell et al. also reported that the rate of referential glancing significantly increased with age. The present study seeks to establish whether gaze alternation between a communicative interactant and a desirable food 1 Referential, in the present context, means that gestures are demonstrably about objects in the environment and is not meant to imply symbolic reference or representation.Correspondence concerning this article should be addressed to David A. Leavens, Department of Psychology, University of Georgia, Athens, Georgia 30602. Electronic mail may be sent to daleavens@aol.com.. Pointing...

Chimpanzees produce numerous species-atypical signals when raised in captivity. Here we report contextual elements of the use of two captivity-specific vocal signals, the "raspberry" and the extended grunt. Results demonstrate that these vocalizations are not elicited by the presence of food; rather the data suggest that these vocalizations function as attention-getting signals. These findings demonstrate a heretofore underappreciated category of animal signals: novel signals invented in novel environmental circumstances. The invention and use of species-atypical signals, considered in relation to group differences in signaling repertoires in apes in their natural habitats, may index a generative capacity in these hominoid species without obvious corollary in other primate species.A heretofore little-studied, yet theoretically important class of animal signals are those produced uniquely within some, but not other populations of the same species. Nowak, Plotkin, and Jansen (2000) listed three putatively exhaustive categories of animal communication designs: "a finite repertoire of calls … ; a continuous analogue signal … ; and series of random variations on a theme" (p. 495). Clearly, the class of novel signals developed by animals is missing from that list. The number of such signals in both the auditory and visual domains is growing rapidly, with recent empirical research into the communicative repertoires of both captive and wild chimpanzees. Wild chimpanzees exhibit a number of group differences in their communicative repertoires, including parametric-as opposed to qualitativedifferences in their vocal repertoires (e.g., Crockford, Herbinger, Vigilant, & Boesch 2004), and qualitative differences in their visual signals, including patchy distribution of the leafclipping display (Nishida, 1980) Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Hostetter et al. 2001; Krause & Fouts 1997;Leavens et al. 2004a;Tomasello, Call, Nagell, Olguin, & Carpenter 1994). In these studies, food is typically placed outside the focal subject's home cage and is therefore out of reach from the subject. In these circumstances, chimpanzees and other great apes only gesture to the food when a human is present and visually oriented toward the subject Hostetter et al. 2001; Krause & Fouts 1997;Leavens, Hopkins, & Bard 1996;Leavens, Hopkins, & Thomas 2004b;Tomasello et al. 1994). Moreover, chimpanzees alternate their gaze between the referent (food) and the social agent while gesturing (Leavens & Hopkins 1998) and "repair" their gestural communication when it has failed (Leavens et al. ...

No abstract