Greg Westergaard - Academia.edu (original) (raw)

Papers by Greg Westergaard

Journal of Medical Primatology, 2003

We examined relationships among cerebrospinal fluid (CSF) concentrations of the major serotonin m... more We examined relationships among cerebrospinal fluid (CSF) concentrations of the major serotonin metabolite (5-HIAA, 5-hydroxyindoleacetic acid) and significant medical and behavioral outcomes for female rhesus macaques. Based on earlier findings with males we predicted that low CSF 5-HIAA concentrations would be associated with a range of negative life history outcomes in our captive specific-pathogen-free (SPF) breeding colony. We found that the mean CSF 5-HIAA concentration among animals that died over the course of the study period was significantly lower than among animals that survived. Further examination indicated an inverse relationship between CSF 5-HIAA concentration and number of treatments for illness, further suggesting a link between serotonergic functioning and overall animal health. Examination of behavioral data indicated that individuals with low CSF 5-HIAA concentrations were more often the targets of aggressive bouts than were individuals with high CSF 5-HIAA concentrations. Finally, we found a positive relationship between CSF 5-HIAA concentration and infant survivorship. These results suggest negative life history consequences of impaired serotonergic functioning in captive female rhesus macaques, and indicate that CSF 5-HIAA concentration sampled early in life may provide a useful tool in facilitating colony management decisions concerning utilization of scarce and increasingly valuable non-human primate resources.

Laterality: Asymmetries of Body, Brain and Cognition, 2002

In the present study we examined the relationship among handedness, immune functioning, and behav... more In the present study we examined the relationship among handedness, immune functioning, and behavioural reactivity in rhesus macaques. We used the absolute number of CD4+ (T-helper) and CD8+ (T-suppressor) cells as dependent measures of immune functioning. We derived reactivity profiles from behavioural responses to a threat, and hand preference profiles from a quadrupedal food-reaching test. The results indicate positive correlations between the frequency of right versus left hand reaches and the absolute number of CD4+ cells, and between the frequency of right versus left hand reaches and the degree of human-directed aggression in response to an invasive threat. Immune measures were not associated with the strength of hand preference. These results are consistent with and extend previous findings obtained with rodents to nonhuman primates and provide further support for the view that behavioural lateralisation is associated with immune functioning and behavioural reactivity.

Veterinary Ophthalmology, 2004

Primates, 1993

The purpose of this research was to examine the influence of age on hand preference in capuchin m... more The purpose of this research was to examine the influence of age on hand preference in capuchin monkeys (Cebus apella). Twenty-two capuchins, aged 6 months to 30 years, were presented with a task that involved reaching for food and a task that involved using sponging tools to absorb juice. Adults exhibited a greater percentage of right-handed actions in each task than did immature subjects. Adults also exhibited a stronger lateral bias than did immature subjects in the sponging task. These results are consistent with hypotheses: a) adult capuchin monkeys are biased toward use of their right hand for reaching; b) adult capuchins exhibit a greater incidence of right-hand preference than do immature capuchins; and c) primates exhibit age-related differences in the strength and direction of hand preference in tasks that involve the use of tools.

Neuropsychologia, 2000

This research examined hand preference and postural characteristics of aimed throwing in capuchin... more This research examined hand preference and postural characteristics of aimed throwing in capuchin monkeys and humans. We sought to directly compare the throwing performances of these primates, particularly the extent to which target distance in¯uences hand preference, throwing posture, and throwing accuracy. For both species we found positive correlations between target distances for throwing accuracy, direction and strength of hand preference, percentage of bipedal vs tripedal throws, and percentage of overarm vs underarm throws. Throwing accuracy did not vary as a function of right vs left hand use although for monkeys throwing accuracy was positively associated with hand preference strength. We noted a sex dierence among humans as males threw more accurately than did females. Between-species analysis indicated that humans exhibited greater right-vs lefthand use, greater hand preference strength, a greater relative percentage of bipedal vs tripedal throws, and a lower relative percentage of overarm vs underarm throws than did monkeys. We believe that the capuchin monkey is an informative nonhuman primate model of aimed throwing in humans and that research examining the throwing behavior of capuchins provides insight into the neurological and behavioral characteristics that underlie coordinated multi-joint movements across the primate order.

Journal of Comparative Psychology, 1996

This research examined hand preference for a bimanual task in 45 tufted capuchin (Cebus apella) a... more This research examined hand preference for a bimanual task in 45 tufted capuchin (Cebus apella) and 55 rhesus macaque (Macaco mulatto) monkeys. Investigators presented subjects with plastic tubes lined with food and noted which hand the animals used to hold the tubes and which hand the animals used to remove the food. Several significant findings emerged from this investigation. First, rhesus macaques, but not tufted capuchins, exhibited a population-level bias toward use of the right hand (although the difference in direction of hand preference between species was not significant). Second, capuchins exhibited greater hand preference strength than did macaques. Third, among capuchins, but not among macaques, hand preference strength was greater for adults than for immatures. Finally, both species used their index digit to remove food most frequently when compared with other digits. Findings of hand preference direction and strength in this study were compared with other findings noted for chimpanzees which performed a bimanual tube task in a previous study. The authors conclude that using the same procedure to compare hand preference across species represents a powerful research tool that can lead to a more complete understanding of the evolution and ontogenesis of primate handedness. The origins of primate handedness are unclear at the present time. Approximately 90% of the human population is right-handed (Annett, 1985), and the corresponding lefthemisphere specialization for manual control is believed to have played a prominent role in lateralization of language and other cognitive functions (Calvin, 1994). MacNeilage, Studdert-Kennedy, and Lindblom (1987) argued that primate handedness evolved through selection pressures that favored lateral bias for postural support and feeding. They hypothesized that primates first evolved a left-hand specialization for visually guided reaching and later a righthand specialization for fine manipulation and bimanual coordination. Several studies have examined hand preference for bimanual tasks in great apes. These studies indicate that chimpanzees, bonobos, and gorillas are biased toward use of their left hand for holding and biased toward use of their

Journal of Comparative Psychology, 1998

Hand preference for quadrupedal and bipedal reaching in humans and rhesus macaques (Macaco mulatt... more Hand preference for quadrupedal and bipedal reaching in humans and rhesus macaques (Macaco mulatto) was examined, and the data were compared with postural reaching data that have been reported for 8 other primate species. Population-level biases were found toward use of the right hand for quadrupedal and bipedal reaching in humans and use of the left hand for quadrupedal reaching in rhesus macaques. Rhesus macaques showed a significant shift toward greater use of the right hand for bipedal vs. quadrupedal reaching. Comparisons with other species showed significant variance in the direction and strength of hand preference across reaching postures. The study noted right-hand biases for bipedal reaching in humans, great apes, and tufted capuchins and shifts toward greater use of the right hand for bipedal vs. quadrupedal reaching in great apes, tufted capuchins, and rhesus macaques. These results suggest that posture alters both the direction and strength of primate hand preference and that bipedalism may have facilitated species-typical right-handedness in humans.

American Journal of Primatology, 1994

ABSTRACT The purpose of this study was to examine the hierarchical complexity of combinatorial ma... more ABSTRACT The purpose of this study was to examine the hierarchical complexity of combinatorial manipulation in capuchin monkeys (Cebus apella). Two experiments were conducted. In Experiment 1 capuchins were presented with an apparatus designed to accommodate the use of probing tools. In Experiment 2 the same capuchins were presented with sets of nesting containers. Five of the ten subjects used probing tools and seven subjects placed objects in the containers. The capuchins' behavior reflected three hierarchically organized combinatorial patterns displayed by chimpanzees and human infants. Although the capuchins sometimes displayed the two more complex patterns (“pot” and “subassembly”), their combinatorial behavior was dominated by the simplest pattern (“pairing”). In this regard capuchins may not attain the same grammar of manipulative action that has been reported for chimpanzees and young human children. © 1994 Wiley-Liss, Inc.

American Journal of Primatology, 2007

Several studies have demonstrated that nonhuman primate males with low cerebrospinal fluid (CSF) ... more Several studies have demonstrated that nonhuman primate males with low cerebrospinal fluid (CSF) levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) exhibit antisocial behavior patterns. Included in these deleterious patterns are impulse control deficits associated with violence and premature death. No studies to date have longitudinally studied the long-term outcome of young subjects with low CSF 5-HIAA concentrations as they mature into adults. In this study we examined longitudinal relations among serotonergic and dopaminergic functioning, as reflected in CSF metabolite concentrations, aggression, age at emigration, dominance rank, and mortality in free-ranging rhesus macaque (Macaca mulatta) males. Our results indicate long-term consistency of individual differences in levels of 5-HIAA in CSF in the subject population from the juvenile period of development through adulthood. We found a significant negative correlation between 5-HIAA concentrations measured in juveniles and rates of high-intensity aggression in the same animals as adults. Further, CSF 5-HIAA concentrations were lower in juveniles that died than in animals that survived. For the young animals that migrated there was a positive correlation between CSF 5-HIAA concentration and age at emigration, whereas for the animals that remained in their troop until later in sexual maturity there was a negative correlation between CSF 5-HIAA concentration and age of emigration. After animals emigrated to a new troop, social dominance rank in the new troop was positively correlated with early family social dominance rank, but inversely correlated with juvenile CSF 5-HIAA concentrations. Taken together, our findings suggest that males with low central serotonin levels early in life delay migration and show high levels of violence and premature death, but the males that survive achieve high rank. These findings indicate that

International Journal of Primatology, 1995

We examined the production of stone tools by capuchins (Cebus apella). Eleven subjects used five ... more We examined the production of stone tools by capuchins (Cebus apella). Eleven subjects used five reduction techniques to produce 346 stone tools (48 cores and 298 flakes). They produced a sharp edge on 83% of the cores and largest flakes. Three monkeys later used a sample of these objects as cutting tools. These results demonstrate that monkeys produce lithic tools analogous to those produced by Oldowan hominids.

doi: 10.1152/japplphysiol.01128.2003 You might find this additional info useful... This article c... more doi: 10.1152/japplphysiol.01128.2003 You might find this additional info useful... This article cites 24 articles, 5 of which you can access for free at:

Primates, 1993

… : Asymmetries of Body, …, 1997

This research investigated the effects of posture on lateral bias for food reaching in tufted cap... more This research investigated the effects of posture on lateral bias for food reaching in tufted capuchin monkeys ( Cebus apella ) by comparing hand preferences for quadrupedal and bipedal reaching. Several findings of this investigation warrant discussion. First, we found a population-level bias towards use of the right hand for bipedal reaching but not for quadrupedal reaching. Second, adults exhibited a greater right-hand preference for bipedal reaching than did immatures. Third, subjects showed a greater right-hand preference, and a greater strength of preference independent of direction, for bipedal reaching than for quadrupedal reaching. Fourth, we found a significant positive relation between the direction of hand preference for quadrupedal and bipedal reaching. We believe that capuchins provide an alternative primate model to chimpanzees for the evolution of human bipedalism and right-handedness. One implication of this model is that right-handedness emerged in hominids prior to extensive expansion of brain size and elaboration of material culture.

Neuropsychopharmacology, 2003

We examined the relations among cerebrospinal fluid (CSF) monoamine metabolite concentrations, pl... more We examined the relations among cerebrospinal fluid (CSF) monoamine metabolite concentrations, plasma hormone concentrations, aggression, and impulsive risk-taking behavior in a free-ranging population of female rhesus macaques. We selected 44 juvenile female rhesus macaques as subjects from a population of approximately 3000 macaques that inhabit a 475-acre Sea Island. We obtained CSF and blood samples, and recorded behavioral observations over

Developmental Psychobiology, 2001

In this research we examined the relationship between plasma cortisol and handedness in infant rh... more In this research we examined the relationship between plasma cortisol and handedness in infant rhesus macaques (Macaca mulatta). Specifically, we tested the hypothesis that stress functioning is related to hemispheric specialization and manifested in a positive correlation between cortisol levels and the frequency of right- versus left- hand use. We found a significant positive relationship between cortisol levels sampled at ages 1 and 3 months and lateral bias toward greater use of the right hand versus left hand sampled between ages 4 and 11 months. Further, we found a significant negative relationship between cortisol sampled at age 5 months and strength of lateral bias (independent of direction). These data suggest an early developmental influence of stress functioning on hemispheric specialization for manual control in infant monkeys.

Child Development, 1997

In this research we examined hand preference in infant rhesus macaques {Macaca mulatta). The subj... more In this research we examined hand preference in infant rhesus macaques {Macaca mulatta). The subjects were 20 Macaca mulatta, each aged between 4 and 11 months. We assessed hand preference using both a unimanual reaching task and a bimanual coordination task. In the unimanual reaching task, we presented subjects with raisins and noted which hand the animals used to retrieve the food. In the bimanual coordination task, we presented the same subjects with plastic tubes filled with raisin paste and noted which hand the animals used to hold the tubes and which hand the animals used to remove the food. We noted a population-level bias toward use of the left hand for both tasks. These results suggest early right hemisphere advantage for reaching and bimanual coordination in Macaca mulatta, although we acknowledge that this issue needs to be examined more directly through neuroimaging procedures such as Positron Emission Tomography (PET) or functional Magnetic Resonance Imaging (fMRI). We speculate that early rightjhemisphere advantage contributes to differ-ential^gattems of hand prefejence development for unimanual and bimanual action, and that the developmerft of hand preference for bimanual coordinatidrTiY related to the emergence of hemispheric specialization for processing species-specific vocalizations.

Journal of Applied …, 2004

Animal models exhibiting high homology with humans at the genetic and pathophysiological levels w... more Animal models exhibiting high homology with humans at the genetic and pathophysiological levels will facilitate identification and validation of gene targets underlying asthma. In the present study, a nonhuman primate model of allergic asthma was developed by sensitizing cynomolgus monkeys to dust mite antigen. Sensitization elevated allergen-specific serum IgE and IgG levels, and peripheral blood mononuclear cells isolated from sensitized animals released IL-4, IL-5, and IL-10, but not IFN-␥. Aerosolized allergen decreased dynamic compliance and induced airway inflammation and hyperresponsiveness to aerosolized histamine. Albuterol and dexamethasone inhibited the airway constriction and allergen-induced inflammation, respectively. Airway wall remodeling that included goblet cell hyperplasia, basement membrane thickening, and smooth muscle hypertrophy was particularly evident in neonatally sensitized animals. In contrast to animals sensitized as adults, neonatally sensitized animals exhibited increased sensitivity to adenosine and larger allergen-induced changes in airway resistance and dynamic compliance. These results demonstrate that sensitization of cynomolgus monkeys with dust mite induces asthmalike symptoms, some of which may be dependent on age at the time of sensitization.

International journal of …, 1998

We examined aimed throwing as a means of food transfer in tufted capuchins (Cebus apella). We con... more We examined aimed throwing as a means of food transfer in tufted capuchins (Cebus apella). We conducted this research in three phases. In Phase 1 we provided food to monkeys in one of two groups housed 1 m apart. We did not provide food to subjects in the second group. An observer recorded each instance in which a subject in the first group threw food toward one in the second group. In Phase 2 we provided a group of capuchins with food and noted each instance in which a subject threw food toward an empty cage. In Phase 3 we provided food simultaneously to two groups of capuchins and noted each instance of food-throwing between them. In Phase 1 subjects in one group threw food toward subjects in a second group, which, when provided the opportunity, did not throw food toward capuchins in the first group. Thrown food was either caught, retrieved, or lost on the test room floor. The rate of throwing decreased significantly when subjects were presented with an empty cage and when both groups of subjects were given food. We propose that psychological processes which underlie aimed throwing and food sharing came into existence through convergent evolution in large-brained, extractive foraging primates. We further speculate that although a well-developed system of exchange, based on contingent reciprocity, may occur among primates only in Homo, simpler transfer systems involving voluntary unidirectional passing of food from one individual to another appear to be more widespread among primates than previously thought and can be expressed in rather unusual circumstances such as those in this experiment.

Animal Cognition, 1998

This research examined token-mediated tooluse in a tufted capuchin monkey (Cebus apella). We cond... more This research examined token-mediated tooluse in a tufted capuchin monkey (Cebus apella). We conducted five experiments. In experiment 1 we examined the use of plastic color-coded chips to request food, and in experiments 2-5 we examined the use of color-coded chips to request tools. Our subject learned to use chips to request tools following the same general pattern seen in great apes performing analogous tasks, that is, initial discrimination followed by an understanding of the relationship among tokens, tools, and their functions. Our findings are consistent with the view that parallel representational processes underlie the tool-related behavior of capuchins and great apes.

Veterinary Ophthalmology, 2004

There is growing evidence for an interaction among fundus pigmentation, character, geography and ... more There is growing evidence for an interaction among fundus pigmentation, character, geography and the function and structure of the outer retina. We examined three inbred groups of rhesus macaques (132 eyes) including all ages. One was a smaller (18 eyes) group. Coat colors were variations of brown-tan however, the smaller group had lighter 'golden' coats and colors. Fundus images were classified for pigmentation and its geographic distribution. In golden-coated animals there was bias toward nasal fundus hypopigmentation with the optic disk as a watershed demarcation zone, which extended in the superior-inferior direction. Temporal fundus hypopigmentation did not occur in the absence of nasal hypopigmentation. More common, darker coated samples showed a characteristic diffuse fundus pigmentation. There was no evidence for albinism or large variations in macular pigmentation. Rhesus monkeys can exhibit geographically controlled genetic development of fundus pigmentation. Hypopigmentation provides for access to the choroidal infrastructure.

Journal of Medical Primatology, 2003

Laterality: Asymmetries of Body, Brain and Cognition, 2002

Veterinary Ophthalmology, 2004

Primates, 1993

Neuropsychologia, 2000

Journal of Comparative Psychology, 1996

Journal of Comparative Psychology, 1998

American Journal of Primatology, 1994

American Journal of Primatology, 2007

International Journal of Primatology, 1995

Primates, 1993

… : Asymmetries of Body, …, 1997

Neuropsychopharmacology, 2003

Developmental Psychobiology, 2001

Child Development, 1997

Journal of Applied …, 2004

International journal of …, 1998

Animal Cognition, 1998

Veterinary Ophthalmology, 2004