Biomedical subjects

W D Hopkins

Publications and source records attributed to W D Hopkins.

At least 19 recordsLinked to original sources

PubMed2000

Birth order and left-handedness revisited: some recent findings in chimpanzees (Pan troglodytes) and their implications for developmental and evolutionary models of human handedness.

This paper examines the relationship between parity, pregnancy outcome, and handedness in a sample of captive chimpanzees (Pan troglodytes). The relation between parity, maternal age and positive or negative pregnancy outcome was assessed from life history data for 536 chimpanzees housed at the Yerkes Regional Primate Research Center. The incidences of negative pregnancy outcome (notably spontaneous abortions and stillbirths) were significantly higher in parities of 8 or higher compared to all other parities. In a sub-sample of 165 chimpanzees, the relation between parity, maternal age and handedness was assessed to determine whether left handedness may serve as a marker of prenatal pathology. These analyses indicated that left-handedness was more prevalent in 1st and 8 or higher parities compared to parities between 2 and 7, respectively. Possible prenatal hormonal and periparturitional factors are discussed as possible mechanisms for the observed findings.

Animals↗

PubMed2000

Asymmetries in cerebral width in nonhuman primate brains as revealed by magnetic resonance imaging (MRI).

A comparative study of asymmetries in cerebral width was conducted in a sample of great apes, Old World and New World monkeys. The brains of all subjects were scanned using magnetic resonance imaging (MRI) and the first axial slice above the third ventricle was identified. Measures of cerebral width were taken at distances of 10% and 30% of the length from the occipital and frontal poles. Cerebral widths were measured from the midline to the lateral surface of the brain for each area. The great apes exhibited a right-frontal and left-occipital directional asymmetry in cerebral width. In contrast, no significant mean directional asymmetries were found in either the Old or New World monkeys. The results in the great apes are consistent with previous reports of petalia asymmetries and suggest that the use of MRI is a valid approach to the assessment of neuroanatomical asymmetries in primates.

Animals↗

PubMed2000

The effect of situational factors on hand preferences for feeding in 177 captive chimpanzees (Pan troglodytes).

This study examined the effect of situational factors on hand use for feeding in a sample of captive chimpanzees. Lateral bias in hand use was tested in biased and unbiased testing circumstances to assess strength and consistency in hand preference. For both unbiased and biased testing conditions, population-level right hand preferences were found for the sample. In the biased condition, subjects were more likely to overcome positional factors in order to feed with their right hand contrasted with the left. Overall, hand use in the biased and unbiased testing conditions was significantly positively correlated. In terms of strength of hand use, juveniles were found to be less lateralized than sub-adults and adults. Moreover, juvenile females were found to be more lateralized than juvenile males. Taken together, the data suggest that chimpanzee hand preferences for feeding are not constrained by situational factors and are relatively consistent in biased and unbiased testing conditions.

Aging↗

PubMed2000

A comparative MRI study of the relationship between neuroanatomical asymmetry and interhemispheric connectivity in primates: implication for the evolution of functional asymmetries.

The authors tested the theory that hemispheric specialization evolved as a consequence of reduced interhemispheric connectivity by examining whether neuroanatomical asymmetries were associated with variation in the ratio of corpus callosum size to brain volume (CC:VOL) and to neocortical surface area (CC:NEO) in human and nonhuman primates. Magnetic resonance images were collected in a sample of 45 primates including 8 New World monkeys, 10 Old World monkeys, 4 lesser apes, 17 great apes, and 6 humans. CC:VOL and CC:NEO were determined and correlated with measures of brain asymmetry. The results indicate that brain asymmetry significantly predicted CC:VOL and CC:NEO. Subsequent analyses revealed that species variation in functional asymmetries in the form of handedness are also inversely related to CC:NEO. Taken together, these results support the hypothesis that leftward brain asymmetries may have evolved as a consequence of reduced interhemispheric connectivity.

Adult↗

PubMed2000

Recognizing facial cues: individual discrimination by chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta).

Faces are one of the most salient classes of stimuli involved in social communication. Three experiments compared face-recognition abilities in chimpanzees (Pan troglodytes) and rhesus monkeys (Macaca mulatta). In the face-matching task, the chimpanzees matched identical photographs of conspecifics' faces on Trial 1, and the rhesus monkeys did the same after 4 generalization trials. In the individual-recognition task, the chimpanzees matched 2 different photographs of the same individual after 2 trials, and the rhesus monkeys generalized in fewer than 6 trials. The feature-masking task showed that the eyes were the most important cue for individual recognition. Thus, chimpanzees and rhesus monkeys are able to use facial cues to discriminate unfamiliar conspecifics. Although the rhesus monkeys required many trials to learn the tasks, this is not evidence that faces are not as important social stimuli for them as for the chimpanzees.

Animals↗

PubMed2000

Chimpanzee (Pan troglodytes) handedness: variability across multiple measures of hand use.

This study examined intertask consistency in handedness across multiple measures of hand use in a sample of 187 chimpanzees (Pan troglodytes). Hand preferences for 2 to 6 measures were collected from the sample, and hand preference scores were derived on the basis of the individual hand preferences for each measure. Seven of 15 possible intratask correlations were significant, with some degree of clustering depending on the motor demands of the tasks. Two overall measures of handedness revealed population-level right-handedness in the chimpanzees, although the degree of bias was reduced for chimpanzees tested on more than 3 measures of hand use. The results are interpreted in the context of several recent studies that proposed theoretical models of handedness in nonhuman primates.

Analysis of Variance↗

PubMed2000

Birth order and hand preference in chimpanzees (Pan troglodytes): implications for pathological models of handedness in humans.

The effect of birth order on hand preference was assessed in a sample of 154 captive-born chimpanzees. Subjects were classified as first, middle, or latter born using 2 classification criteria based on their birth order. Hand preference was measured using a task that elicited coordinated bimanual actions. Significant birth-order effects were found for both classification criteria, with first- and latter-born subjects exhibiting a lesser degree of right-handedness compared with middle-born subjects. These data suggest that biological rather than sociological factors play a greater role in explaining the observed birth-order effects on hand preference in humans.

Analysis of Variance↗

PubMed2000

Sylvian fissure asymmetries in nonhuman primates revisited: a comparative mri study.

Magnetic resonance images (MRI) were collected in a sample of 28 apes, 16 Old World monkeys and 8 New World monkeys. The length of the sylvian fissure (SF) and the superior temporal sulcus (STS) was traced in each hemisphere from three regions of the cerebral cortex. These three regions were labeled according to their position on the sagittal plane as lateral, medial and insular. It was hypothesized that the length and asymmetry of these fissures would be dependent on the region of measurement and that a leftward asymmetry in the SF and STS would be more robust in the great ape sample than for the monkeys. The results indicated within the ape sample a population-level leftward asymmetry in the medial and insular regions of the SF. Within the Old and New World monkey samples, the SF was leftward in the medial region at the population level, but not at the insular region. Additionally, the Old World monkeys exhibited a population-level rightward lateral SF and a rightward lateral STS. No other families exhibited population-level asymmetries in the lateral region of the SF or in any region of the STS. These results are consistent with findings reported in apes and, to a lesser extent, monkeys. MRI has excellent potential for comparing neuroanatomy across taxonomic families that will help future investigations.

Animals↗

PubMed2000

A longitudinal study of hand preference in chimpanzees (Pan troglodytes).

A longitudinal study of hand preferences was assessed in a sample of 53 captive chimpanzees. Four measures of laterality assessed during the first 3 months of life were correlated with three measures of hand preferences assessed when the subjects were between 2 and 5 years of age. In addition, the effect of rearing environment on juvenile hand preferences was assessed in a larger sample of 83 chimpanzees. Overall, some early asymmetries were predictive of juvenile hand preferences, notably head orientation and hand-to-hand activities, and a defensive grasping response. No significant effects of rearing on hand preferences were found but males were more right-handed than females for two of the three juvenile measures. The results are discussed within the context of different developmental models of hand preference in humans.

Animals↗

PubMed1999

Heritability of hand preference in chimpanzees (Pan troglodytes): evidence from a partial interspecies cross-fostering study.

Heritability of hand preference was tested in a sample of 188 chimpanzees (Pan troglodytes). Hand preference was measured by coordinated bimanual actions, and concordance percentages were compared between parents and offspring and siblings. Among siblings, concordance percentages were compared for dyads in which both individuals were raised by chimpanzees, both were raised by humans, or 1 was raised in each environment. The results indicated population-level right hand preferences for coordinated bimanual actions. There were no significant associations in hand preference between parents and offspring. In full and maternal half siblings, concordance in hand preference was significantly greater than chance in mother- and human-reared individuals but not in cross-fostered dyads. The cumulative results suggest that the direction of hand preference is heritable in chimpanzees but the mechanism of transmission is not genetic. Several environmental explanations are proposed to explain the findings, including the potential role of maternal cradling bias and in utero fetal position.

Animals↗

PubMed1999

The whole-hand point: the structure and function of pointing from a comparative perspective.

Pointing by monkeys, apes, and human infants is reviewed and compared. Pointing with the index finger is a species-typical human gesture, although human infants exhibit more whole-hand pointing than is commonly appreciated. Captive monkeys and feral apes have been reported to only rarely "spontaneously" point, although apes in captivity frequently acquire pointing, both with the index finger and with the whole hand, without explicit training. Captive apes exhibit relatively more gaze alternation while pointing than do human infants about 1 year old. Human infants are relatively more vocal while pointing than are captive apes, consistent with paralinguistic use of pointing.

Animal Communication↗

PubMed1998

Planum temporale asymmetries in great apes as revealed by magnetic resonance imaging (MRI).

The planum temporale (PT), a portion of Wernicke's area, is important for linguistic functions in humans and is larger in the left compared to the right hemisphere. In this study, we assessed the presence and size of the PT in a sample of non-human primates including 21 great apes, four lesser apes, 11 Old World monkeys and eight New World monkeys using magnetic resonance imaging. The PT was measured in both the sagittal and coronal planes by use of multiplanar reformatting software. The PT could only be identified in the sample of great apes and not in the remaining non-human primate species. Within the great ape sample, the PT was larger in the left hemisphere than in the right in a statistical majority of the subjects. These results are consistent with the notion that the PT evolved as a definable structure about 15 million years ago and may have arisen as a result for selection for greater cortical folding which in turn led to greater gyrification in larger brains.

Animals↗

PubMed1998

Maternal cradling and infant nipple preferences in rhesus monkeys (Macaca mulatta).

This study investigated lateral biases in nipple preferences, maternal cradling, carrying, and retrieval in 41 rhesus macaque (Macaca mulatta) mother-infant dyads living in two captive social groups. Observations were made during the first 6 weeks of infant life using a combination of scan sampling and ad-libitum sampling techniques. Infants exhibited a significant left-nipple preference in the first weeks of life but the bias decreased with infant age. Mothers showed a left-arm bias in carrying their infants but no significant lateral bias in cradling or retrieval. Our results suggest that the left-side cradling bias reported in studies of humans and some other primates reflects a bias in the infant's nipple preference rather than in maternal behavior. The infants' preference for the left nipple is consistent with both Salk's (1960) heartbeat hypothesis and with more recent hypotheses linking this lateral bias with brain asymmetry and hemispheric specialization for mother-infant communication.

Age Factors↗

PubMed1998

Intentional communication by chimpanzees: a cross-sectional study of the use of referential gestures.

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.

Animal Communication↗

PubMed1998

Lateralized changes in tympanic membrane temperature in relation to different cognitive tasks in chimpanzees (Pan troglodytes).

Lateralized changes in tympanic membrane (TM) temperature were assessed in chimpanzees. Subjects were engaged in 1 of 3 different cognitive tasks, including matching-to-sample, visual-spatial discrimination, and a motor task. During execution of each task, TM temperatures were taken from each ear over a 20-min time period. The TM temperatures at each time interval were subtracted from a baseline measure to assess relative change in blood flow. For the matching-to-sample and visual-spatial discrimination tasks, significant lateralized changes in TM temperature were found, with left-ear temperature increasing and right-ear temperature decreasing. No laterality effects were found for the motor or control tasks. These data provide the first evidence of laterality in physiological functioning in chimpanzees and suggest that transient asymmetries in cognitive functions are associated with changes in cerebral blood flow as assessed by TM temperature change.

Animals↗

PubMed1998

Hand use and gestural communication in chimpanzees (Pan troglodytes).

Hand use in gestural communication was examined in 115 captive chimpanzees (Pan troglodytes). Hand use was measured in subjects while they gestured to food placed out of their reach. The distribution of hand use was examined in relation to sex, age, rearing history, gesture type, and whether the subjects vocalized while gesturing. Overall, significantly more chimpanzees, especially females and adults, gestured with their right than with their left hand. Foods begs were more lateralized to the right hand than pointing, and a greater prevalence of right-hand gesturing was found in subjects who simultaneously vocalized than those who did not. Taken together, these data suggest that referential, intentional communicative behaviors, in the form of gestures, are lateralized to the left hemisphere in chimpanzees.

Animal Communication↗

PubMed1998

Why faces may be special: evidence of the inversion effect in chimpanzees.

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 automobiles were also used. The stimuli were presented in a sequential matching-to-sample (SMTS) format using a computerized joystick-testing apparatus. Subjects performed better on upright than inverted stimuli in all classes. Performance was significantly better on upright than inverted presentations of chimpanzee and human faces but not on capuchin monkey faces or automobiles. These data support previous studies in humans that suggest the inversion effect occurs for stimuli for which subjects have developed an expertise. Alternative explanations for the inversion effect based on the type of spatial frequency contained in the stimuli are also discussed. These data are the first to provide evidence for the inversion effect using several classes of face stimuli in a great ape species.

Animals↗

PubMed1997

Haptic discrimination in capuchin monkeys (Cebus apella): evidence of manual specialization.

Two experiments investigated the effects of haptic and visual discrimination on hand preference in 22 brown capuchin monkeys (Cebus apella). The percentage of left-handed subjects in Experiment 1 were 63.6%, 45.5%, and 18.2% for haptic, bipedal, and quadrupedal reaching, respectively. In Experiment 2, the haptic demands of the task were manipulated by using additional food types and another tactile medium. Left-hand preferences were further strengthened when reaching into water compared to pineshavings in Experiment 1. Reaching with no tactile interference resulted in equal numbers of lateralized and nonlateralized subjects. These results show that when reaching demands the use of haptic cues, as opposed to visual ones, monkeys shift towards greater left hand use. This is consistent with what is known about right hemisphere superiority for haptic discrimination in humans.

Aging↗