William D. Hopkins

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Hand preference for a coordinated bimanual task was assessed in a sample of 110 chimpanzees (Pan troglodytes). Subjects were presented with opaque tubes, the inside of which was coated with peanut butter. The hand and finger used to extract the peanut butter was recorded in 2 test sessions. A population right-hand bias was found. Juvenile and adolescent(More)
Five chimpanzees were tested on their ability to discriminate faces and automobiles presented in both their upright and inverted orientations. The face stimuli consisted of 30 black and white photographs, 10 each of unfamiliar chimpanzees (Pan troblodytes), brown capuchins (Cebus apella), and humans (Homo sapiens). Ten black and white photographs of(More)
I describe methodological and statistical issues in the assessment of hand preference in nonhuman primates and discuss them in the context of a recent paper by McGrew and Marchant (1997) in which they conclude that there is no convincing evidence of population-level hand preferences in nonhuman primates. The criteria used by them to evaluate individual and(More)
This study examined the communicative behavior of 49 captive chimpanzees (Pan troglodytes), particularly their use of vocalizations, manual gestures, and other auditory- or tactile-based behaviors as a means of gaining an inattentive audience's attention. A human (Homo sapiens) experimenter held a banana while oriented either toward or away from the(More)
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(More)
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(More)
Hand preference in reaching was assessed under 2 postural adjustment conditions in 40 chimpanzees (Pan troglodytes) and 9 orangutans (Pongo pygmaeus). The postural conditions were quadrupedal and upright, during which reaching for food was scored on a minimum of 50 trials. Results indicated no population preference during quadrupedal reaching but a(More)
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(More)
Pointing has long been considered to be a uniquely human, universal, and biologically based gesture. However, pointing emerges spontaneously, without explicit training, in captive chimpanzees. Because pointing is commonplace in captive chimpanzees and virtually absent in wild chimpanzees, and because both captive and wild chimpanzees are sampled from the(More)
Historically, population-level handedness has been considered a hallmark of human evolution. Whether nonhuman primates exhibit population-level handedness remains a topic of considerable debate. This paper summarizes published data on handedness in great apes. Comparative analysis indicated that chimpanzees and bonobos show population-level right(More)