Comparison of the physical characteristics of grooming in two species of macaques (Macaca nemestrina and M. radiata).

Examined social grooming in groups of bonnet and pigtail macaques to test the hypothesis that the physical aspects of grooming (body sites, postures, methods) evolved in more aggressive species of primates to serve social functions (proximity maintenance and tension reduction). Both species used social presents to direct grooming to particular sites, and used grooming to other sites to terminate interactions, thus regulating proximity with grooming to certain body sites. The 2 species differed in method of grooming: Pigtails primarily stroked (method used for tension reduction); bonnets picked or pick-stroked (method used for hygiene). Pigtail but not bonnet grooming method regulates tension reduction. Pigtails groomed in a social context, whereas bonnets groomed in solitary context. The pigtail results are similar to those found with rhesus monkeys. Different aspects of grooming serve different functions. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Recognition of heterospecific alarm vocalization by Bonnet Macaques (Macaca radiata).

Recognition of heterospecific alarm vocalizations is an essential component of antipredator behavior in several prey species. The authors examined the role of learning in the discrimination of heterospecific vocalizations by wild bonnet macaques (Macaca radiata) in southern India. The bonnet macaques' flight and scanning responses to playbacks of their own alarm vocalizations were compared with their responses to playbacks of vocalizations of Nilgiri langurs (Trachypithecus johnii), Hanuman langurs (Semnopithecus entellus), and sambar deer (Cervus unicolor). The study was conducted in 3 regions that differed in the frequency with which bonnet macaques encountered these species and included an urban setting. Call recognition was highest in adults and in regions where individuals were frequently exposed to the calling species; calls were not recognized by urban monkeys. Thus, age and experience are important factors in heterospecific call recognition by bonnet macaques. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Affiliative vocalizations in infant rhesus macaques (Macaca mulatta).

In Exp 1, infant rhesus monkeys were separated and then reunited with mothers, united with a male, or placed into an empty cage. Infants girned more when with mothers or the male than when alone. Girns declined over time when infants were united with the male. Coo rates were high when the infant was alone or with the male. Shrieks, barks, and fear-related behavior were higher with the male. In Exp 2, the vocalizations of infants were examined during separation when alone or when mothers or a male were in the same room. Infants cooed more when mothers or a male were present. Cooing increased over time, with a greater increase in the mothers' presence. Girns were given to both mothers and males, but more were given to mothers. Coos and girns are both affiliative vocalizations but are differentially modulated as infants cease cooing when they receive contact comfort. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Hiding and perspective taking in long-tailed macaques (Macaca fascicularis).

Seven long-tailed macaques (Macaca fascicularis) were trained by threes not to drink from a juice nipple as long as an experimenter was facing them. However, they were allowed to drink when the experimenter was standing with his or her back turned. During transfer tests, the monkeys had a choice between 2 juice nipples, one uncovered and the other hidden from the experimenter by a wooden screen, while the experimenter was facing them. We tested whether the monkeys would then prefer to drink behind the screen, thus demonstrating that they transferred knowledge acquired during training. Results did not yield a significant outcome, suggesting that the macaques did not transfer the observable "experimenter's visible open eyes" and that they did not take the experimenter's perspective. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

New methodology applied to bonnet macaques (Macaca radiata) to address some contradictory evidence on manual asymmetries in old world monkeys.

Seven bonnet macaques (Macaca radiata) with strong hand preferences in performing a computer-generated joystick task that required directing a cursor to contact a small stationary target on a monitor were given comparable experience with each hand on the task over a 5-week period. Hand use was randomly restricted to either only the left or only the right hand across trials by automatically inputting into a computer the unique identification numbers of microchips implanted in the forearms of each macaque. Subsequent presentation of a novel task requiring maintenance of contact between a cursor and a moving target revealed no performance difference between preferred and nonpreferred hands or between left and right hands on the basis of number of errors or time to complete the task. The findings suggest that the strong hand preference for these tasks does not derive from a performance advantage for the preferred hand. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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

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. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cued repetition of self-directed behaviors in macaques (Macaca nemestrina).

Two macaques (Macaca nemestrina) were trained to perform 3 self-directed behaviors on signal and to repeat behaviors after a 'repeat' signal. The cognitive processes underlying the monkeys' repeat performance were evaluated via multiple repetitions of the repeat signal, extended delay periods between target behavior and repeat signal, and by transferring the repeat signal to novel behaviors. The monkeys seemed to use representations of their own past behaviors as a basis for repetition performance, but they mostly failed to correctly repeat target behaviors after extended delays and during transfer tasks. Implications for episodic memory abilities are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of pattern recognition in infant pigtailed macaques (Macaca nemestrina).

Examined the development of pattern recognition in 31 infant pigtailed macaques using the familiarization–novelty technique. Ss were familiarized with 2 identical black and white patterns and tested on the familiar pattern paired with a novel one. Cross-sectional data revealed that a novelty preference occurred with increasing age. Younger Ss (mean age 178 days postconception or 1 postnatal week) did not show a reliable visual preference for either the novel or the familiar patterns. Infants with a mean age of 203.2 days postconception (about 4 postnatal weeks) fixated novel patterns significantly longer than familiar ones. Data suggest that by 200 days postconception, infant macaques are able to remember some aspects of previously exposed stimuli and will perform consistently on a familiarization–novelty task. Results are discussed in relation to the development of human infant pattern-recognition abilities. Pigtailed macaques provide an excellent model for the investigation of human infant recognition memory, 1 wk of maturation in the pigtailed infant being equivalent to 1 mo in the human. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Covert visual search: A comparison of performance by humans and macaques (Macaca mulatta).

The duration of the visual search by human participants for visual features is independent of the number of targets being viewed. In contrast, search for targets formed by conjunction of features is characterized by reaction times (RTs) that increase as a linear function of the number of items viewed, suggesting that the target detection requires scrutiny of the search array by focal attention. Macaque (Macaca mulatta) and human performance on feature and conjunction search tasks was compared in 7 human Ss and 5 female monkeys by using color or motion, or by conjunctions of color and motion. Like human participants, monkeys exhibited a dichotomy between feature and conjunction search performance. This finding suggests that humans and macaques engage similar brain mechanisms for representation of feature and conjunction targets. This behavioral paradigm can thus be used in neurophysiological experiments directed at the mechanisms of feature integration and target selection. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral observations of sensory substitution in neonate macaques (Macaca arctoides).

The ability of neonate macaque monkeys to learn to respond to artificial spatial sensory information was studied through the use of compact, head-worn, electronic spatial sonars with audible displays, which translate spatial information into auditory dimensions specifying distance, direction, and surface characteristics. Three animals were born in the dark and raised without vision for 1 to 3 months while wearing either the Binaural Sensory Aid (Animal 1; Kay, 1974) or the Trisensor (Animals 2 and 3; Easton & Jackson, 1983) airborne sonars. Each animal demonstrated alertness to information transmitted by the devices in spontaneous reaching or reinforced discrimination tasks, and more device-related, perceptual-motor activities were observed when the sensors were switched on than when they were switched off. The results show that neonate monkeys can learn effective use of information obtained from sensory substitution devices through unstructured interaction with the environment. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Complex learning by low-birth-weight and normal-birth-weight juvenile pigtailed macaques (Macaca nemestrina).

As a group, human low-birth-weight (LBW) infants are at risk for a range of developmental problems including intellectual deficits later in life. However, in human studies it is difficult to separate the effects of LBW from the effects of socioeconomic status and competence of caregivers. In order to eliminate such confounding variables, we studied complex learning by LBW and normal-birth-weight (NBW) juvenile pigtailed macaques. The animals were given a battery of learning tasks, which included nonmatch-to-sample, match-to-sample, and a conditional test in which the color of the stimulus board dictated whether the problem was nonmatch- or match-to-sample. NBW subjects showed reliably better performance than LBW subjects on all three tasks. LBW performance was influenced by the relative novelty and familiarity of the correct and incorrect stimuli, with familiar stimuli consistently preferred over novel stimuli. These results suggest that LBW infants may use different strategies than NBW infants in solving such problems. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Visual recognition memory in high- and low-risk infant pigtailed macaques (Macaca nemestrina).

Pigtailed macaque infants were administered a series of visual recognition problems adapted from a standardized test developed for use with human infants. The subjects were classified as either low risk or high risk. The low-risk animals were normal, whereas the high-risk animals had developmental problems (e.g., hypoxia, failure-to-thrive) that sometimes are correlated with cognitive deficits later in life in humans. The test consisted of a series of problems in which two identical abstract black-and-white patterns were presented for a study period, followed by a two-part test trial in which the previously exposed pattern was paired with a novel one. Looking time to each target was recorded. The low-risk group easily differentiated novel from previously seen targets. The high-risk group gave no evidence of recognition. The results have implications for an animal model to examine factors contributing to intellectual deficits in human infants. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An experimental investigation of referential looking in free-ranging Barbary macaques (Macaca sylvanus).

The authors examined looking behavior between 15 Barbary macaque (Macaca sylvanus) infants and their mothers in the presence of a rubber snake (experimental period) and in the absence of the snake (control period). Two of the 15 infants looked referentially at their mother in the experimental period. Including both referential and nonreferential looks, the six older infants (aged 5 to 12 months) displayed a higher frequency of looks to mother than nine younger infants (aged 3 to 4.5 months) in the experimental period, but not in the control period. Older infants looked more to the mother in the experimental condition, whereas the younger infants looked more to the mother in the control condition, or looked equally in the two conditions. These results suggest that age is an important factor in determining looking behavior to mother in situations of uncertainty. Compared to hand-reared chimpanzees or human infants tested in standard social referencing paradigms, the infant macaques displayed a low rate of referential looking. Possible explanations for this are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit and explicit category learning by macaques (Macaca mulatta) and humans (Homo sapiens).

An influential theoretical perspective differentiates in humans an explicit, rule-based system of category learning from an implicit system that slowly associates different regions of perceptual space with different response outputs. This perspective was extended for the 1st time to the category learning of nonhuman primates. Humans (Homo sapiens) and macaques (Macaca mulatta) learned categories composed of sine-wave gratings that varied across trials in bar width and bar orientation. The categories had either a single-dimensional, rule-based solution or a two-dimensional, information-integration solution. Humans strongly dimensionalized the stimuli and learned the rule-based task far more quickly. Six macaques showed the same performance advantage in the rule-based task. In humans, rule-based category learning is linked to explicit cognition, consciousness, and declarative reports about the contents of cognition. These results demonstrate an empirical continuity between human and nonhuman primate cognition, suggesting that nonhuman primates may have some structural components of humans’ capacity for explicit cognition. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Acquisition of discrimination learning of patterns identical in configuration in macaques (Macaca mulatta and M. fuscata).

Compared the acquisition of discrimination of 5 pairs of pattern cues in a Wisconsin General Testing Apparatus by 223 naive macaque monkeys. The pairs of discriminanda were identical in configuration but varied slightly in either the size of the cue or the size of the background plaque; thus, the degree of separation of the cue from the fringe of the plaque, the response site, was slightly different for each pair of discriminanda. These small differences in cue–response separation had marked effects on the rate of acquisition of the discriminations. Even an increment of separation as small as 0.5 cm resulted in a retardation of the acquisition. This retardation was due to prolonged performance at the chance level and not to a slow rate of improvement from the chance to a criterion level. The finding indicates that the difficulty in the acquisition learning on pattern tasks depends largely on the difficulty of attending to the pattern cues at small cue–response separations. (45 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Behavioral asymmetries of psychomotor performance in rhesus monkeys (Macaca mulatta): A dissociation between hand preference and skill.

Hand preferences were recorded for 35 rhesus monkeys as they manipulated a joystick in response to 2 computerized tasks. These preferences were then used to contrast 8 left- and 10 right-handed Ss on performance measures of hand skill. Individual hand preferences were found, but no significant population asymmetry was observed across the sample. However, the performance data reveal substantial benefits of right-handedness for joystick manipulation, as this group of monkeys mastered the 2 psychomotor tasks significantly faster than did their left-handed counterparts. The data support earlier reports of a right-hand advantage for joystick manipulation and also support the importance of distinguishing between hand preference and manual performance in research on functional asymmetries. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of familiarization time on visual recognition memory in infant pigtailed macaques (Macaca nemestrina).

Used the familiarization-novelty procedure in 2 experiments to examine the effects of study time on visual recognition memory in 34 infant pigtailed macaques. In Exp I, Ss were familiarized with abstract black-and-white patterns for 10 sec. They then were given a test trial in which the familiar stimulus was paired with a novel one. Results show that during the test trial, Ss directed significantly more visual attention toward the novel stimulus, a finding that provides evidence for recognition memory. In Exp II, a different group of Ss was familiarized with abstract black-and-white patterns for 1, 5, and 10 sec. Ss demonstrated recognition after the 10-sec familiarization period. Ss older than 6 wks of age at test also demonstrated recognition after the 5-sec study time, a finding that is consistent with the hypothetical 4:1 ratio between macaque and human infant development of some basic sensory, perceptual, and cognitive processes. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of small cue–response separation on pattern discrimination in macaques (Macaca fuscata and M. mulatta).

Three studies with 17 macaque and 6 rhesus monkeys examined the effect of small cue–response separations on Ss' pattern discriminations. When training on a pattern discrimination with a cue–response separation was discontinued during performance at the chance level, there was no saving on the rate of learning a 2nd task (with identical cues but a different cue–response separation) relative to the performance of naive control Ss. By contrast, when training was discontinued at a performance level a little better than chance, there was significant saving on learning a 2nd task. After learning the 2nd task, a 3rd task with new pattern cues was learned, with marked saving on the duration of performance at the chance level. Results indicate that during the initial stage of performance at the chance level, monkeys do not attend to cues if there is even a small separation between the cue and the response site. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effect of posture on hand preference during experimental food reaching in bonobos (Pan paniscus).

The effect of posture on hand preferences was examined in an experiment with 5 bonobos (Pan paniscus). To obtain a food reward, the animals had to adopt 1 out of 7 different postures. These postures represented an increasing problem to the maintenance of body equilibrium. It was expected that an increasing demand for equilibrium maintenance would elicit individual preferences and a population-level bias. All animals showed an increasing trend toward left-handedness while shifting to a bipedal posture from a seated posture by way of a quadrupedal posture. The importance of bipedalism in the evolution of left- and right-handedness is discussed briefly. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Dominance fades with distance: An experiment on food competition in long-tailed macaques (Macaca fascicularis).

Dominant animals often can suppress the competitive behavior of subordinates by overt aggression or by their mere presence. This experiment on pairs of long-tailed macaque females explored whether this effect of dominant animals is influenced by interindividual distance. A dominant and a subordinate, but stronger, animal could compete for food by a tug-of-war on a bar. The animals were separated by 2 grids, spaced at either 30 or 100 cm. At 30 cm, 7 of 8 subordinate subjects either did not pull the bar or did not obtain a major share of the available food. In contrast, at 100 cm, all subordinate subjects obtained more food than the dominant. Thus, the dominant animal could suppress the competitive behavior of the subordinate only at the short interindividual distance, despite the fact that the dominant could not approach or attack even at the short distance and could be fully seen by the subordinate even at the large distance. (PsycINFO Database Record (c) 2010 APA, all rights reserved)