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William D Hopkins

Publications and source records attributed to William D Hopkins.

At least 37 records · Page 2Linked to original sources
PubMed2005

Individual and setting differences in the hand preferences of chimpanzees (Pan troglodytes): a critical analysis and some alternative explanations.

Several recent papers have been critical at a theoretical and empirical level of the evidence of population-level right-handedness in chimpanzees and other great apes. For example, Palmer (2002) has recently argued that the evidence of population-level handedness in chimpanzees is weak because there are sampling biases in the data. McGrew and Marchant (1997) argue that all the evidence of right-handedness in apes is from captive animals and therefore the observed phenomenon has little ecological validity. In this paper, we address recent issues regarding the presentation and interpretation of other hand preference data and argue that chimpanzees are right-handed for some measures. We further argue that purported differences in hand use between wild and captive chimpanzees due to rearing environments are unfounded and we emphasise that more cooperative work between researchers working in captive and feral populations is needed to facilitate collection of data on common measures of hand preference.

Animals↗
PubMed2005

Chimpanzees are right-handed when recording bouts of hand use.

Whether nonhuman primates exhibit population-level handedness remains a topic of considerable debate. Previous research has shown that chimpanzees are right-handed when frequencies of hand use are recorded but some have questioned the validity of this approach. In this study, we evaluated handedness in 180 captive chimpanzees for a task measuring bimanual actions. Bouts rather than frequency of hand use were recorded in each subject. Population-level right-handedness was found using both continuous and nominal scales of measurement. Neither sex nor rearing history had a significant effect on hand use. These results indicate that chimpanzees are right-handed, even when using a more conservative measure of handedness. Limitations in the use of bouts in handedness assessment are also discussed.

Animal Population Groups↗
PubMed2005

The distribution and development of handedness for manual gestures in captive chimpanzees (Pan troglodytes).

This article describes the distribution and development of handedness for manual gestures in captive chimpanzees. Data on handedness for unimanual gestures were collected in a sample of 227 captive chimpanzees. Handedness for these gestures was compared with handedness for three other measures of hand use: tool use, reaching, and coordinated bimanual actions. Chimpanzees were significantly more right-handed for gestures than for all other measures of hand use. Hand use for simple reaching at 3 to 4 years of age predicted hand use for gestures 10 years later. Use of the right hand for gestures was significantly higher when gestures were accompanied by a vocalization than when they were not. The collective results suggest that left-hemisphere specialization for language may have evolved initially from asymmetries in manual gestures in the common ancestor of chimpanzees and humans, rather than from hand use associated with other, non-communicative motor actions, including tool use and coordinated bimanual actions, as has been previously suggested in the literature.

Age Factors↗
PubMed2004

Further evidence of a right hand advantage in motor skill by chimpanzees (Pan troglodytes).

Asymmetries in motor skill when grasping small food items was evaluated in a sample of captive chimpanzees. In two experiments, error rates in grasping food were assessed when controlling for individual differences in grip morphology. In both experiments, chimpanzees were found to make more errors with the left compared to the right hand. Male chimpanzees were also found to make more errors compared to females. These results are discussed in the context of a presumed disassociation between hand preference and performance as indicators of cerebral dominance in motor functions.

Analysis of Variance↗
PubMed2004

Referential communication by chimpanzees (Pan troglodytes).

Two experiments were conducted to assess the referential function of chimpanzee (Pan troglodytes) gestures to obtain food. The chimpanzees received 1 trial per condition. In Experiment 1 (N = 101), in full view of the chimpanzee, a banana was placed on top of 1 of 2 inverted buckets or was hidden underneath 1 of the buckets. In Experiment 2 (N = 35), 4 conditions were presented in constant order: (a) no food, no observer; (b) no food, observer present; (c) food present, no observer; and (d) food present, observer present. Gestures and visual orienting were used socially and referentially. The capacity for nonverbal reference may predate the Hominidae-Pongidae split, and the development of nonverbal reference may be independent of human species-specific adaptations for speech.

Animal Communication↗
PubMed2004

Chimpanzees (Pan troglodytes) are predominantly right-handed: replication in three populations of apes.

Population-level right-handedness has historically been considered a hallmark of human evolution. Even though recent studies in chimpanzees (Pan troglodytes) have demonstrated population-level right-handedness for certain behaviors, some have questioned the validity and consistency of these findings by arguing that reported laterality effects are specific to certain colonies of apes and to those chimpanzees reared by humans. The authors report evidence of population-level right-handedness in 3 separate colonies of chimpanzees. Moreover, handedness in the 3 colonies was unrelated to the proportion of subjects that were raised by humans. This is the strongest evidence to date that population-level handedness is evident in chimpanzees and is not an artifact of human rearing.

Animals↗
PubMed2004

Handedness in chimpanzees (Pan troglodytes) is associated with asymmetries of the primary motor cortex but not with homologous language areas.

The neurobiology of hand preferences in nonhuman primates is poorly understood. In this study, the authors report the first evidence of an association between hand preference and precentral gyrus-morphology in chimpanzees (Pan troglodytes). Hand preferences did not significantly correlate with other asymmetric brain regions associated with language functions in humans including the planum temporale and frontal operculum. The overall results suggest that homologous regions of the motor cortex control hand preferences in humans and apes and that these functions evolved independently of left-hemisphere specialization for language and speech.

Age Factors↗
PubMed2004

Asymmetries in the hippocampus and amygdala of chimpanzees (Pan troglodytes).

Magnetic resonance imaging was used to measure the hippocampal and amygdalar volumes of 60 chimpanzees (Pan troglodytes). An asymmetry quotient (AQ) was then used to calculate the asymmetry for each of the structures. A one-sample t test indicated that there was a population-level right hemisphere asymmetry for the hippocampus. There was no significant population-level asymmetry for the amygdala. An analysis of variance using sex and rearing history as between-group variables showed no significant main effects or interaction effects on the AQ scores; however, males were more strongly lateralized than females. Several of these findings are consistent with results found in the human literature.

Amygdala↗
PubMed2004

Human assessment of chimpanzee facial asymmetry.

In this study, facial asymmetry in chimpanzees was assessed using a technique that has traditionally been implemented in human studies. Image composites made of each half of chimpanzees' facial expressions were presented to humans with and without chimpanzee experience. The group of subjects with chimpanzee experience considered composites made of the left side of the chimpanzee faces as the most emotionally intense for the emotional categories of play, silent bared-teeth, scream face, and a neutral category. On the other hand, left-left composites were not consistently judged by subjects with and without chimpanzee experience as the most similar to the whole original face, which might be explained as the result of an attentional bias in the human observers towards the right side of the chimpanzee expressions. Furthermore, responses given by subjects with and without chimpanzee experience were highly correlated, which indicates that the two groups of humans perceived the chimpanzee facial expressions in a similar fashion. The finding of left-sided asymmetries in these chimpanzees' facial expressions suggests a right hemisphere asymmetry in the production of emotions in this species and it is consistent with results reported in human and other nonhuman primates.

Adult↗
PubMed2003

Are planum temporale and sylvian fissure asymmetries directly related? A MRI study in great apes.

In humans and great apes, both the planum temporale (PT-part of Wernicke's area) and the sylvian fissure (SF) in the left cerebral hemisphere have been consistently shown to be larger than the corresponding structures in the right hemisphere. The greater length of the SF in the left hemisphere is commonly thought to be a direct consequence of the larger expansion of the PT in the same hemisphere. However, there is a lack of studies that have attempted to directly assess the tenability of this hypothesis. To address this lack of data, we collected magnetic resonance images (MRI) of the brain in 28 apes. The surface area of the PT and the length of the pre- and post-central SF were measured in each hemisphere using image acquisition and analysis software. In accordance with previous findings, the PT was markedly larger in the left hemisphere than in the right, and there was also a leftward asymmetry of the SF, particularly of its post-central section. However, we found no statistically significant correlation between asymmetry of the PT and of the post-central SF, whereas we did find evidence of a positive association between asymmetry of the post-central SF and of the inferior parietal lobe. These results are congruent with those of a recent study with human subjects [Neuropsychiatry, Neuropsychology and Behavioral Neurology 12 (1999) 1]. Overall, this converging evidence leads us to question the widely accepted notion of a direct relationship between PT and SF asymmetries and to consider possible implications of this finding for the study of the evolutionary origin of PT asymmetry in primates.

Animals↗
PubMed2003

Comparative assessment of handedness for a coordinated bimanual task in chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus).

Hand preferences for a coordinated bimanual task were assessed in a sample of 31 captive gorillas (Gorilla gorilla) and 19 captive orangutans (Pongo pygmaeus) and were compared with chimpanzee (Pan troglodytes) hand preferences in subjects that were matched on the basis of age, sex, and rearing history. The task required that the apes remove food from the inside edges of a symmetrical polyvinyl chloride pipe presented to them in their home cages. The results indicate significant species differences with chimpanzees showing population-level right-handedness and orangutans showing population-level left-handedness. The gorillas showed a nonsignificant trend toward right-handedness. The results are discussed in terms of possible ecological or biomechanical factors that may influence hand preferences in different ape species.

Animals↗
PubMed2002

Matching visual stimuli on the basis of global and local features by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta).

This study was designed to examine whether chimpanzees and monkeys exhibit a global-to-local precedence in the processing of hierarchically organized compound stimuli, as has been reported for humans. Subjects were tested using a sequential matching-to-sample paradigm using stimuli that differed on the basis of their global configuration or local elements, or on both perceptual attributes. Although both species were able to discriminate stimuli on the basis of their global configuration or local elements, the chimpanzees exhibited a global-to-local processing strategy, whereas the rhesus monkeys exhibited a local-to-global processing strategy. The results suggest that perceptual and attentional mechanisms underlying information-processing strategies may account for differences in learning by primates.

Animals↗
PubMed2002

Asymmetry in facial expression of emotions by chimpanzees.

Asymmetries in human facial expressions have long been documented and traditionally interpreted as evidence of brain laterality in emotional behavior. Recent findings in nonhuman primates suggest that this hemispheric specialization for emotional behavior may have precursors in primate evolution. In this study, we present the first data collected on our closest living relative, the chimpanzee. Objective measures (hemimouth length and area) and subjective measures (human judgements of chimeric stimuli) indicate that chimpanzees' facial expressions are asymmetric, with a greater involvement of the left side of the face in the production of emotional responses. No effect of expression type (positive versus negative) on facial asymmetry was found. Thus, chimpanzees, like humans and some other nonhuman primates, show a right hemisphere specialization for facial expression of emotions.

Animals↗
PubMed2002

The effect of thought structure on the production of lexical movements.

This study was designed to test the hypothesis that participants who are expressing a thought that is encoded spatially will use more lexical movements than participants who are expressing a thought that is encoded textually. The 37 participants were divided into two groups and instructed to either watch a cartoon or read a description of the cartoon. Their video-taped responses were analyzed for the frequency and laterality of both lexical and motor movements. Members of the video group did use more lexical movements than members of the written group, and the right hand was dominant in the production of lexical movements made by members of both groups. These data support the theory that lexical movements are integrally related to the speech production process.

Female↗
PubMed2002

Grip morphology and hand use in chimpanzees (Pan troglodytes): evidence of a left hemisphere specialization in motor skill.

Three experiments on grip morphology and hand use were conducted in a sample of chimpanzees. In Experiment 1, grip morphology when grasping food items was recorded, and it was found that subjects who adopted a precision grip were more right-handed than chimpanzees using other grips. In Experiment 2, the effect of food type on grasping was assessed. Smaller food items elicited significantly more precision grips for the right hand. In Experiment 3, error rates in grasping foods were compared between the left and right hands. Significantly more errors were made for the left compared with the right hand. The cumulative results indicate that chimpanzees show a left-hemisphere asymmetry in motor skill that is associated with the use of precision grips.

Animals↗
PubMed2002

Gestural communication in chimpanzees (Pan troglodytes): the influence of experimenter position on gesture type and hand preference.

This study examined the influence of experimenter position on hand use in gestural communication in a sample of 127 captive chimpanzees. Hand use in gestural communication was recorded while an experimenter was positioned either left, right, or directly in front of the subject. The type of gesture was also recorded as either a food beg or whole hand point. Both hand use and gesture were consistent across experimenter positions. Overall, a significant population-level right hand bias was found, particularly for food beg gestures. These results are consistent with previous findings in chimpanzees and suggest that lateralisation in gestural communication is left hemisphere dominant.

Journal Article↗
PubMedDate not supplied

Functional asymmetry of emotions in primates: new findings in chimpanzees.

In the past 15 years, there have been a number of studies conducted on asymmetries in the perception and production of facial expressions in human and non-human primates as a means of inferring hemispheric specialization for emotions. We review these studies to assess continuity and discontinuity between species in these emotional processes. We further present new data on asymmetries in the production of facial expressions in a sample of captive chimpanzees. Objective measures (hemimouth length and area) and subjective measures (human judgement's of chimeric stimuli) indicate that chimpanzees' facial expressions are asymmetric, with a greater involvement of the left side of the face (right hemisphere) in the production of emotional responses. Left hemimouth was bigger than the right in the facial expressions of pant-hooting, play, and silent bared-teeth (p < 0.05) and it extended laterally more than the right in the categories of pant-hooting, silent bared-teeth, and scream face (p < 0.05). Human judges also reported that the left side of the faces was emotionally more intense in the case of the play and silent bared-teeth categories (p < 0.01). Thus, chimpanzees, like humans and some other non-human primates, show a right hemisphere specialization for facial expression of emotions, which suggests that this functional asymmetry is homologous in all these species.

Animals↗