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)     

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)     

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)     

Development of cross-modal recognition in infant pigtail monkeys (Macaca nemestrina).

Examined the development of cross-modal recognition in 48 infant pigtail monkeys in 2 studies by using an adaptation of the visual preference technique. Ss were first familiarized orally with pacifiers of 1 of 2 shapes and were then tested on corresponding visual stimuli. In a cross-sectional experiment (Exp I), Ss under 200 days postconception at test (approximately 4 postnatal weeks) showed a visual preference for the orally familiar stimuli, which provided evidence for cross-modal recognition. Ss over 200 days postconception at test showed a visual preference for 1 of the test stimuli, which made their data uninterpretable with respect to cross-modal abilities. In a longitudinal experiment (Exp II), Ss were tested once when they were younger than 200 days postconception and once when they were older. When young, they showed a visual preference for the orally familiar stimuli. When older, they showed a visual preference for the same test stimuli found for the cross-sectional Ss. Results are discussed relative to human infant cross-modal data obtained by similar procedures. (19 ref) (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)     

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)     

Development of visual responsiveness in Macaca nemestrina monkeys.

Administered a battery of tests for assessing visual responsiveness to 69 pigtail monkeys 2 days to 6 mo of age. Age changes were found on all tests. None of the responses could be consistently elicited at birth. Tests involving simple sensory capacities and orienting motor responses generally appeared first. Tasks requiring more complicated sensory processing or motor responses emerged at progressively older ages. By 5 wks after birth, normal Ss ordinarily responded positively on all tests. The battery is therefore a convenient and effective screening tool for assessing whether a young monkey has normal vision. Age norms are presented in terms of the percent of Ss at each age expected to respond positively on each test. Results are compared to the development of analogous responses in human infants. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Sexual arousal in male pigtailed monkeys (Macaca nemestrina): Effects of serial matings by two males.

Examined male sexual arousal in 4 vasectomized male and 3 intact multiparous female pigtailed monkeys with the postejaculatory interval (PEI) used as the dependent variable. 12 paired trials were conducted in which a male and female copulated, the 1st male was removed and a 2nd male was or was not allowed to copulate with the female, and the 1st male was again permitted to copulate with the female. In male–female pairs, the PEI was shortened by 60% of normal (control) values if the male observed another male copulating with his female partner. Results demonstrate that the normal PEI is not an absolute male refractory period; males are capable of copulating sooner, and they will do so when presented with certain behavioral stimuli. A long PEI may prevent males from disrupting their own plugs prematurely, whereas a short PEI may result from a premature disruption of the plug by another male. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

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)     

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)     

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)     

Social learning in pig-tailed macaques (Macaca nemestrina) and adult humans (Homo sapiens) on a two-action artificial fruit.

An artificial fruit (AF) was used to test for social learning in pig-tailed macaques (Macaca nemestrina) and adult humans (Homo sapiens). A monkey demonstrator opened the AF, showing alternative methods to 2 groups of cage mates. Video films of the monkey demonstrations were presented to adult humans. Compared with chimpanzees and children, the macaques watched the demonstrations significantly less and in a much more sporadic manner. They also produced only very weak and transitory evidence of social learning. In contrast, the adult humans performed as one might expect of optimum imitators, even producing evidence of components of a "ratchet effect." (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interhemispheric transfer of visual discriminations in split-chiasm monkeys (Macaca nemestrina) and its measurement.

The interhemispheric transfer of visual discriminations in split-chiasm monkeys (Macaca nemestrina) was assessed by training with one eye to a criterion level, then testing either with that same eye (control) or with the other eye (transfer). The difference between these 2 values was the loss due to transfer. A computer simulation suggested that the usual savings score could grossly misestimate transfer ability. In addition, stimuli with comparable left and right halves were used to minimize the effect of the bilateral hemianopia caused by chiasm section. Performance with the untrained eye was slightly, but statistically significantly, poorer than with the trained eye. No evidence of the phenomena of "learning to transfer" was found (i.e., there was no improvement in transfer ability in relation to concurrent intrahemispheric controls). (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)     

Contrasting the edge- and surface-based theories of object recognition: Behavioral evidence from macaques (Macaca mulatta).

This study assessed the contribution of edge and surface cues on object representation in macaques (Macaca mulatta). In Experiments 1 and 2, 5 macaques were trained to discriminate 4 simple volumetric objects (geons) and were subsequently tested for their ability to recognize line drawings, silhouettes, and light changes of these geons. Performance was above chance in all test conditions and was similarly high for the line drawings and silhouettes of geons, suggesting the use of the outline shape to recognize the original objects. In addition, transfer for the geons seen under new lighting was greater than for the other stimuli, stressing the importance of the shading information. Experiment 3, using geons filled with new textures, showed that a radical change in the surface cues does not prevent object recognition. It is concluded that these findings support a surface-based theory of object recognition in macaques, although it does not exclude the contribution of edge cues, especially when surface details are not available. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of auditory and visual interference on auditory-visual delayed matching-to-sample in monkeys (Macaca fascicularis).

Two monkeys were trained on an auditory-visual (AV) delayed matching-to-sample (DMS) task with auditory cues serving as sample stimuli and visual cues serving as comparison stimuli. To determine whether the monkeys were remembering auditory or visual information during the delay period, auditory and visual interference were presented following the sample stimulus. Auditory interference had little effect on AV DMS performance. In contrast, visual interference severely impaired AV DMS performance, indicating that the monkeys were remembering visual information during the delay period. This finding may reflect a predisposition of monkeys toward remembering information via their dominant visual modality. (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)     

Kin preferences in primates (Macaca nemestrina): Relatedness or familiarity?

90 1.5–3.5-yr-old female pigtail macaques were given 2-choice preference tests involving stimulus monkeys varying in relatedness and familiarity to the S. Related Ss had consanguinity coefficients of at least .25, while unrelated Ss had coefficients of .05 or less. Familiar Ss had lived together for 80% of the time since their birth, whereas unfamiliar Ss had lived together less than 5% of their lives. The hypotheses tested were that (a) relatedness adds a positive bias to preferences based on familiarity and (b) in the absence of familiarity, monkeys will prefer a related social partner. Data fail to support either hypothesis. Only familiarity was effective in producing social preferences, with kinship producing neither an independent nor an additive influence. These results argue against a primate "phenotypic matching" mechanism by which related animals prefer one another because of genetic physical or behavioral similarities even though they have had no prior social contact. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of selective neonatal temporal lobe lesions on socioemotional behavior in infant rhesus monkeys (Macaca mulatta).

Normal infant monkeys and infant monkeys with neonatal damage to either the medial temporal lobe or the inferior temporal visual area were assessed in dyadic social interactions at 2 and 6 months of age. Unlike the normal infant monkeys, which developed strong affiliative bonds and little or no behavioral disturbances, the lesioned monkeys (each of which was observed with an unoperated control) exhibited socioemotional abnormalities and aberrant behaviors. The socioemotional changes predominated at 6 months of age and were particularly severe in monkeys with medial temporal lesions. In both the pattern and time course, the socioemotional deficits produced by the neonatal medial temporal lesions bear a striking resemblance to the behavioral syndrome in children with autism. Further analysis of these lesion-induced abnormalities in nonhuman primates may therefore provide insight into this debilitating human developmental disorder. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Video-task assessment of learning and memory in macaques (Macaca mulatta): Effects of stimulus movement on performance.

Effects of stimulus movement on learning, transfer, matching, and short-term memory performance were assessed with 2 monkeys using a video-task paradigm (VTP) in which the animals responded to computer-generated images by manipulating a joystick. Performance on tests of learning set, transfer index, matching to sample, and delayed matching to sample in the VTP was comparable to that obtained in previous investigations using the Wisconsin General Testing Apparatus (D. M. Rumbaugh et al, 1989). Additionally, learning, transfer, and matching were reliably and significantly better when the stimuli or discriminanda moved than when the stimuli were stationary. External manipulations such as stimulus movement may increase attention to the demands of a task, which in turn should increase the efficiency of learning. Findings have implications for the investigation of learning in other populations, as well as for the application of the VTP to comparative study. (PsycINFO Database Record (c) 2010 APA, all rights reserved)