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PubMed2001

Haematology and blood chemistry of Cebus apella in relation to sex and age.

An effective health care program entails the prevention, diagnosis and treatment of medical problems. A knowledge of baseline values in clinically normal individuals is essential for determining the limits between good health and disease and for understanding the changes produced by pathogenic agents. However, very little information is currently available concerning the blood chemistry and haematological values of different species of monkeys, particularly new-world primates. The values of some haematological and chemical parameters in Cebus apella were determined. The aim of the present work was to verify the effect of age and sex on normal blood values. Blood samples were collected once a year for two successive years from 36 monkeys living in large captive social groups. Significant differences between males and females were found for AST, GGT, urea nitrogen and creatinine, erythrocytes, haemoglobin and haematocrit. Significant differences between juveniles and adults were found for calcium, AST, alkaline phosphatase, inorganic phosphorus, glucose, neutrophils, lymphocytes and serum protein parameters.

Aging↗
PubMed2003

How do tufted capuchin monkeys (Cebus apella) understand causality involved in tool use?

Four tufted capuchin monkeys (Cebus apella) were trained to choose from 2 hook-like tools, 1 of which successfully led to collecting food, whereas the other did not because of inappropriate spatial arrangement of the tool and the food. In Experiment 1, all of the monkeys successfully learned the basic task. The monkeys performed successfully with tools of novel colors and shapes in Experiments 2-5. These results demonstrate that the monkeys used the spatial arrangement of the tool and the food as a cue. However, they failed when there were obstacles (Experiment 6) or traps (Experiment 7) on the path along which the monkeys dragged tools. These results may suggest that capuchin monkeys understand the spatial relationship between 2 items, namely, food and the tool, but do not understand the spatial relationship among 3 items, namely, food, tool, and the environmental condition. The possible role of stimulus generalization is also considered.

Animals↗
PubMed2005

Ordinal representation of numeric quantities by brown capuchin monkeys (Cebus apella).

Using techniques established by E. M. Brannon and H. S. Terrace (2000) with rhesus macaques (Macaca mulatta), the authors tested the ability of brown capuchins (Cebus apella) to order arrays of items ranging in quantity from 1 to 9. Three monkeys were trained on a touch screen to select the quantities 1-4 in ascending order. The monkeys exhibited successful transfer of this ability to novel representations of the quantities 1-4 and to pairs of the novel quantities 5-9. Patterns of responding with respect to numeric distance and magnitude were similar to those seen in human subjects, suggesting the use of similar psychological processes. The capuchins demonstrated an ordinal representation of quantity equivalent to that shown in Old World monkeys.

Animals↗
PubMed2005

What perceptual rules do capuchin monkeys (Cebus apella) follow in completing partly occluded figures?

Capuchin monkeys (Cebus apella) matched a variety of rodlike figures, distinguishable only by their central portions. The monkeys were then tested for perceptual completion rules by examining which comparison figures they would choose as matching the sample with the critical central portion occluded by a horizontal belt. In Experiment 1, the monkeys overwhelmingly chose a straight rod over disconnected rods and rods having irregular shapes at their center, irrespective of the presence-absence of common motion of visible parts of the samples. The monkeys chose a connected rod for relatable rods and disconnected rods for non-relatable ones in Experiment 2. In Experiments 3 and 4, some of the monkeys chose rods specified by the global regularity of the contour, whereas others did not. Experiment 5 showed that humans and capuchin monkeys basically follow similar perceptual rules in completing occluded contours, but the global regularity rule may be stronger in humans.

Adult↗
PubMed2005

Auditory--visual cross-modal perception of communicative stimuli in tufted capuchin monkeys (Cebus apella).

Research on cross-modal performance in nonhuman primates is limited to a small number of sensory modalities and testing methods. To broaden the scope of this research, the authors tested capuchin monkeys (Cebus apella) for a seldom-studied cross-modal capacity in nonhuman primates, auditory-visual recognition. Monkeys were simultaneously played 2 video recordings of a face producing different vocalizations and a sound recording of 1 of the vocalizations. Stimulus sets varied from naturally occurring conspecific vocalizations to experimentally controlled human speech stimuli. The authors found that monkeys preferred to view face recordings that matched presented vocal stimuli. Their preference did not differ significantly across stimulus species or other stimulus features. However, the reliability of the latter set of results may have been limited by sample size. From these results, the authors concluded that capuchin monkeys exhibit auditory-visual cross-modal perception of conspecific vocalizations.

Acoustic Stimulation↗
PubMed1990

Hand preference and performance on unimanual and bimanual tasks in capuchin monkeys (Cebus apella).

Patterns of manual preference and the extent to which preference provided a benefit in performance (movement time) were evaluated in 7 young adult capuchin monkeys (Cebus apella). Directions of preference were inconsistent within individual animals across home-cage activities, unimanual, and bimanual experimental tasks. Preferences were more strongly expressed in the experimental tasks than in the home cage. A left bias in the population for prehension, predicted by recent theories, was not evident in any setting. Movement time was moderately negatively correlated with degree of preference within experimental tasks. The benefit to performance conferred by lateral preference was not dependent on whether the right or left hand was preferred. Lateralization of prehension appears to be a flexible process in these monkeys, which can result in quickly realized benefits in some conditions.

Animals↗
PubMed1991

Hand preference in the use and manufacture of tools by tufted capuchin (Cebus apella) and lion-tailed macaque (Macaca silenus) monkeys.

The purpose of this study was to examine hand preference in the use and manufacture of probing tools by tufted capuchin and lion-tailed macaque monkeys (Cebus apella and Macaca silenus). Hand preference for the tool-using sequence was noted in 4 of 5 capuchins (a left-hand preference was noted in 3 ss) and 3 of 4 macaques (a left-hand preference was noted in 2 ss). The monkeys frequently used bimanual action in the initial and final segments of the 3-component task and typically modified tools through coordinated action of the hands and teeth. These data provide evidence consistent with the hypotheses that (a) hemisphere specialization for manual control evolved in primates prior to intensive use of tools by early hominids and (b) monkeys prefer the left hand for precise, visually guided, manipulative actions.

Animals↗
PubMed1991

Generative aspects of manipulation in tufted capuchin monkeys (Cebus apella).

Evaluating the cognitive and ontogenetic bases of tool use in primates requires comparative data on the generative nature of manipulation, including the frequency and variety of combinations of actions and objects. Thirty-one tufted capuchins (Cebus apella) of 3 age groups devoted significant proportions of time to interaction with objects and substrates. Activity that combined an object with a substrate occurred often; activities that combined 2 portable objects were less frequent. Predictions drawn from neo-Piagetian theory of an ontogenetic link between combinatorial behaviors and the onset of tool use were not supported. The frequency and generative nature of capuchins' manipulative activity, particularly acts combining objects and substrates, could account for their proclivity to use tools. The use of tools by capuchins need not involve the representational abilities proposed by neo-Piagetian theory.

Age Factors↗
PubMed1994

Lack of comprehension of cause-effect relations in tool-using capuchin monkeys (Cebus apella).

Four tufted capuchin monkeys (Cebus apella), successful in a tool task in which they used a stick to push a reward out of a tube, were tested in a similar task, with a tube with a hole and a small trap. Depending on where the stick was inserted, the reward was pushed either out of the tube or into the trap. With the trap-tube task, we assessed whether the monkeys understood the cause-effect relation between their behavior and the outcome. In Experiment 1, each subject underwent 14 10-trial blocks with the trap tube. Three subjects performed at chance level. The 4th subject's (Rb) performance improved, reaching 95% success in the last 6 blocks. In Experiment 2, Rb received additional tests to investigate its successful strategy further. Rb solved the trap-tube task by means of a distance-based, associative rule. The performances of the 4 subjects indicate that they did not take into account the effects of their actions on the reward.

Animals↗
PubMed1995

Performance in a tool-using task by common chimpanzees (Pan troglodytes), bonobos (Pan paniscus), an orangutan (Pongo pygmaeus), and capuchin monkeys (Cebus apella).

Performance by individual animals of three species of great apes (Pan troglodytes, Pan paniscus, and Pongo pygmaeus) and capuchin monkeys (Cebus apella) was assessed by presenting a food treat inside a clear tube. The subjects readily used a straight stick to obtain the food. When sticks were bundled together, the apes immediately unwrapped the bundle to obtain an individual stick, whereas capuchins attempted to insert the bundled sticks. When a misshapen stick was provided, apes, but not capuchins, showed an improvement in terms of modifying the misshapen stick before insertion. Our results indicate that all these species can solve these tasks. However, only the performance of apes is consistent with emerging comprehension of the causal relations required for the avoidance of errors in the more complex tasks.

Animals↗
PubMed1995

Patterns of individual diet choice and efficiency of foraging in wedge-capped capuchin monkeys (Cebus olivaceus).

Capuchin monkeys (Cebus olivaceus) exhibit extensive intragroup variability in foraging and diet. To consider how age, sex, and individual identity contribute to this variability, the authors examined foraging and diet in 18 wedge-capped capuchin monkeys in 1 social group in the wild. Age-sex classes did not differ in the time spent ingesting food, the reliance on plant foods, the foraging actions used or substrates exploited, or in the efficiency of exploiting animal foods. They did differ, however, in the time spent finding food, time devoted to animal foods and to vigorous foraging, and the efficiency of foraging. The sexes differed more than age groups. Individual differences within age-sex class were less extensive than expected and were more evident in juveniles than adults. Within-group variability in foraging reflected catholic selection and equivalent treatment of substrates by all individuals, rather than individual specializations.

Age Factors↗
PubMed1996

Hand preference for a bimanual task in tufted capuchins (Cebus apella) and rhesus macaques (Macaca mulatta).

This research examined hand preference for a bimanual task in 45 tufted capuchin (Cebus apella) and 55 rhesus macaque (Macaca mulatta) 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.

Age Factors↗
PubMed1997

Transfers of food from adults to infants in tufted capuchins (Cebus apella).

This study examined the behavioral mechanisms that support transfer of food from adults to infants in tufted capuchins (Cebus apella). Two captive groups of capuchins were presented with abundant quantities of unshelled pecans or commercial pellets. Five of 11 infant subjects could not open the nuts. A variety of tolerated interactions were initiated by infants toward adults, and food was frequently transferred. All such interactions were more frequent with nuts (a preferred food) than with pellets. Adult capuchins were equally tolerant of infant capuchins that could open nuts and those that could not. Tolerated interactions during feeding could result in acquisition of dietary information by young capuchins or to important, if intermittent, nutritional support.

Aging↗
PubMed1997

Developmental changes in manipulation in tufted capuchins (Cebus apella) from birth through 2 years and their relation to foraging and weaning.

This study examined the contributions of physical and sensorimotor development to manipulation in capuchins (Cebus apella) from birth to 2 years. Between months 1-6 and 7-12, manipulation increased significantly in frequency, in the proportion that was vigorous or required fine motor control, and in the proportion directed at portable objects. Fine motor control, moving objects in relation to the body, and stamina are largely in place by 12 months, after which little changed. All elements of the manipulative repertoire have appeared, and vigorous and dexterous activities have peaked before fully independent foraging. Emergence of permanent dentition and achievement of approximately half of adult body size accompany the attainment of fully independent foraging at 15 months. Thereafter, increasing strength and specific knowledge probably contribute more to changing foraging competence in young capuchins than do stamina and sensorimotor development.

Aging↗
PubMed1998

Why some capuchin monkeys (Cebus apella) use probing tools (and others do not).

Tufted capuchins (Cebus apella) were provided with a task that facilitated the use and modification of sticks as probing tools. It was found that subjects aged 10 years or older at initial task exposure were less likely to use tools than were younger subjects. Furthermore, juveniles whose mothers died before the subjects were aged 3 years were less likely to use tools than were juveniles whose mothers survived through this period. The ability to use tools was not related to subject sex or to access to the tool site or raw tool materials. Subjects modified tools both before and during their use, and the relative percentage of tools modified increased with subject age. Thus, it appears that capuchins most readily acquire tool use before the age of 10 years and that early disruption of the mother-infant relationship has deleterious effects on the emergence of instrumental behavior.

Aging↗
PubMed1999

Visual list memory in capuchin monkeys (Cebus apella).

Memory of 3 capuchin monkeys, Cebus apella, was tested with lists of 4 travel-slide pictures and different retention intervals. They touched different areas of a video monitor to indicate whether a test picture was in a list. At short retention intervals (0 s, 1 s, 2 s), memory was good for the last list items (recency effect). At a 10-s retention interval, memory improved for 1st list items (primacy effect). At long retention intervals (20 s and 30 s), primacy effects were strong and recency effects had dissipated. The pattern of retention-interval changes was similar to rhesus monkeys, humans, and pigeons. The time course of recency dissipation was similar to rhesus monkeys. The capuchin's superior tool-use ability was discussed in relation to whether it reflects a superior general cognitive ability, such as memory. In terms of visual memory, capuchin monkeys were not shown to be superior to rhesus monkeys.

Animals↗
PubMed1999

Strategies used to combine seriated cups by chimpanzees (Pan troglodytes), bonobos (Pan paniscus), and capuchins (Cebus apella).

The authors investigated strategies used to combine seriated cups by apes (Pan troglodytes and P. paniscus) and monkeys (Cebus apella) using a protocol reported in P. M. Greenfield, K. Nelson, and E. Saltzman's (1972) study with children. It was hypothesized that apes would exhibit more hierarchical combinations of cups than monkeys, given apes' language capacity, and that apes would seriate the cups more efficiently than monkeys. As predicted, apes made many structures with the cups using a variety of strategies, and monkeys rarely combined the cups. After a training phase to orient monkeys to the task, the 2 genera did not differ in the strategies used to combine the cups or in efficiency in seriating the cups. Success in this task suggests that sensorimotor versions of hierarchically organized combinatorial activity are well within apes' and monkeys' abilities.

Animals↗
PubMed2000

Learning and limits of use of eye gaze by capuchin monkeys (Cebus apella) in an object-choice task.

The ability of 3 capuchin monkeys (Cebus apella) to use experimenter-given cues to solve an object-choice task was assessed. The monkeys learned to use explicit gestural and postural cues and then progressed to using eye-gaze-only cues to solve the task, that is, to choose the baited 1 of 2 objects and thus obtain a food reward. Increasing cue-stimulus distance and introducing movement of the eyes impeded the establishment of effective eye-gaze reading. One monkey showed positive but imperfect transfer of use of eye gaze when a novel experimenter presented the cue. When head and eye orientation cues were presented simultaneously and in conflict, the monkeys showed greater responsiveness to head orientation cues. The results show that capuchin monkeys can learn to use eye gaze as a discriminative cue, but there was no-evidence for any underlying awareness of eye gaze as a cue to direction of attention.

Animals↗