Chimpanzee (Pan troglodytes) pointing: Hand shapes, accuracy, and the role of eye gaze.

Abstract

The manual pointing of 2 signing chimpanzees, Moja and Tatu, was examined in 2 experiments. Experiment 1 investigated eye-gaze direction, hand use, and hand shape while pointing. Both chimpanzees obtained the attention of a human before pointing toward an unreachable object. During 100 trials, the chimpanzees alternated their eye gaze between the object and the human while pointing. Moja's points were left-hand biased, and Tatu showed no lateral hand bias. Both indexical and whole hand points were recorded. Experiment 2 tested the chimpanzees' ability to point accurately toward objects in close proximity to each other. Humans were able to reliably determine the locations toward which the chimpanzees pointed. Both chimpanzees showed left-hand biases, and a higher proportion of indexical points were observed than in Experiment 1. These results are compared and contrasted with recent hypotheses pertaining to the topography of chimpanzee pointing and the role of eye gaze in deictic interactions.

Learned vocal and breathing behavior in an enculturated gorilla

“…These learned sounds included an unvoiced raspberry and also a voiced extended grunt, described as a low, loud, guttural sound made with the mouth open (also see Krauss and Fouts 1997, which noted the use of a raspberry as an attention getter by a sign-taught chimpanzee).…”

Now you see me, now you don't: evidence that chimpanzees understand the role of the eyes in attention

“…In studies intended to determine what chimpanzees understand about the attentional states of others, investigators have typically compared the gestural and vocal behavior produced by a focal subject when an experimenter or conspecific is attending to the chimpanzee (e.g., facing the animal, making eye contact, and/ or engaging in species typical head movements) to the behavior produced when the experimenter or conspecific is not attending to the chimpanzee. Several studies have found evidence that chimpanzees differentiate between an attentive audience and an inattentive audience, such that they direct more visual gestures (e.g., species typical begging gestures made with the hand extended outward and palm oriented up) toward an individual who is oriented toward them than toward an experimenter who is oriented away from them (Hostetter et al 2001;Kaminski et al 2004;Krause and Fouts 1997;Leavens et al 2004;Liebal et al 2004;Tomasello et al 1994). …”

Usage and comprehension of manual gestures in wild chimpanzees

“…Leavens et al (2004) also found that the rate of gesture production increased when an experimenter was looking at the chimpanzees. Krause and Fouts (1997a) have shown that chimpanzees used attention-getting behaviours such as vocalisations and auditory gestures to attract the experimenter"s attention before employing pointing or other visual gestures.…”

“…have reported that the visual gestures of wild and captive gorillas were produced more often than tactile or auditory gestures when the recipient was looking at a signaller. Krause and Fouts (1997a) found that chimpanzees used attention getting behaviours such as vocalisations and auditory gestures to attract the experimenter"s attention before employing pointing or other visual gestures.…”

“…signallers display sensitivity to the presence of an audience when producing their gestures (Leavens et al, 2004). Signallers are sensitive to the recipient"s attentional state, gesturing more often when recipient is already looking at them (Tomasello and Camaioni, 1997), as well as using attention-getting behaviour in absence of visual attention from recipients (Krause and Fouts, 1997b). While these studies have shown flexible use of gestures in response to both the presence and visual attention of an audience, a more compelling set of supporting evidence for complex cognitive skills underlying gestural communication comes from reports of communicative persistence and elaboration.…”