Gradual acquisition of visual discrimination tasks in a social group of rhesus monkeys (Macaca mulatta)

An established, captive colony of 74 rhesus monkeys (Macaca mulatta) was group-tested on a simultaneous visual discrimination problem and three reversals of the initial discrimination. The task incorporated important aspects of rhesus foraging behavior. Although other studies of communal groups of nonhuman primates have reported rapid learning, subjects in the present study showed no evidence of one-trial acquisition of the initial problem or of rapid learning-set formation across the reversal series. Instead, mean and individual performance, on all variables measured, improved gradually, both within and across series. Subjects appeared to “learn how to learn,” consistent with findings of traditional studies of individual discrimination learning. Our finding of gradual learning in group-living animals argues that the source of rapid learning in previous reports is not attributable to social influence or ecological relevance, but may reflect specific procedural or species differences between studies.     

Short-term memory for haptic cues in monkeys (Macaca mulatta)

Short-term memory (STM) for haptic information was examined in a delayed matching-to-sample (DMTS) task. Three rhesus monkeys were tested in DMTS with all possible combinations of different-size spheres and cubes as the sample and comparison stimuli. The results showed that the decrease in percentage correct as a function of the retention intervals was relatively independent of the size and shape of the sample and comparison stimuli. In general, at each retention interval, percentage correct was higher when the (1) comparison stimuli differed in both size and shape than when the comparison stimuli differed in only size or shape, (2) size differences between the comparison stimuli increased, and (3) samples were spheres rather than cubes. This pattern of results suggests that dimensions of the haptic stimuli influenced discrimination but had little effect on the animals’ STM. In Experiment 2, the same three monkeys responded to the sample and comparison stimuli with the same hand or responded to the sample with one hand and the comparison stimuli with the opposite hand. The decrease in percentage correct across retention intervals was comparable for all possible hand combinations. These results suggest that the loss of information from STM is comparable when the sample and comparison stimuli are both felt with the same hand or with opposite hands.     

恒河猴和食蟹猴血糖和胆固醇的比较

采用全自动血液生化分析仪测定了488例恒河猴(Macaca mulatta)和795例食蟹猴(Macaca fascicularis)的血糖和胆固醇两项指标,并比较了年龄、性别和地区差异,以及两种猴之间的差异.结果表明除个别组CHOL雌性高于雄性外(P＜0.05),多数组无性别差异;两种猴GLU和CHOL的值与年龄和营养水平显著相关.两种猴之间存在显著差异的组为GLU幼年组和CHOL全部组.     

Deficits in visual recognition in low birth weight infant pigtailed monkeys (Macaca nemestrina)

15 low birth weight and 15 normal birth weight pigtailed monkey infants were administered an adaptation of a standardized test of visual recognition memory, originally developed for human infants. Animals were given a series of problems in which 2 identical black-and-white patterns were presented for a familiarization period. The previously exposed pattern was then paired with a novel one, and looking time to each pattern was recorded. The normal birth weight animals directed a significant amount of their visual attention to the novel stimuli, thus demonstrating recognition abilities. As a group, the performance of the low birth weight infants remained at chance. These findings have important implications for an animal model to examine factors contributing to poor cognitive outcome in low birth weight human infants.     

Crying and infant abuse in rhesus monkeys

This study investigated the relation between crying and infant abuse in group-living rhesus monkeys (Macaca mulatta). The subjects were 10 abusive mothers with their infants and 10 control mother-infant pairs. Abused infants cried more frequently than controls in the first 12 weeks of life, even when cries immediately following abuse were excluded from the analysis. The coos of 5 abused infants differed from those of 5 controls in several acoustic parameters, whereas their screams and geckers were acoustically similar, when recorded in the same context. Abusive mothers were less likely than control mothers to respond positively to the cries of their infants. Although infant cries may increase the probability of abuse being repeated, infant crying per se does not appear to be a major determinant of abuse.     

Effects of sample duration and spaced repetition upon delayed matching-to-sample in monkeys (Macaca arctoides andSaimiri sciureus)

Delayed matching-to-sample was used to study the effects of sample presentation time and spaced repetition upon delayed matching accuracy in one stumptail monkey and three squirrel monkeys. It was found in Experiment 1 that presenting the sample stimulus for 0.5 sec led to lower matching accuracy than was the case with longer presentation times of 2.5, 5.0, and 10.0 sec. Experiments 2 and 3 investigated the effects of temporally spacing the presentations of the sample stimulus. It was found that spaced repetition led to a deterioration of performance relative to massed repetition. These results are similar to the findings of experiments with pigeons and are contradictory to several previous experiments with monkeys or apes which found no effect of presentation time and a facilitative effect of spaced repetition. It is suggested that the use of monkeys inexperienced in short sample duration matching and tested in operant chambers using a limited set of noncomplex stimuli may be responsible for the discrepancies between these results and those of other experiments with primates.     

Airblast avoidance learning sets in rhesus monkeys

Five rhesus monkeys were tested across a series of object discrimination problems requiring avoidance of noxious pressurized air. Each S displayed a progressive reduction in the number of trials to reach criterion on particular problems, eventually achieving 82% and 88% correct performance on Trials 2–6 and Trial 6. respectively. Certain error factors also appearing in appetitive discrimination learning set research (stimulus perseveration and differential cue) were identified, as well as a factor of relative unimportance in appetitive set (positional responding). A most persistent appetitive error factor presumably reflecting a tendency to explore the unchosen object (response shift) did not appear. In addition, the results extend the effectiveness of aversive airblasts to a relatively complex discrimination task.     

Responses of water snakes (Natrix r. rhombifera) and garter snakes (Thamnophis sirtalis) to chemical cues

In a series of simultaneous two-choice preference tests, water snakes (Natrix r. rhombifera) displayed a significant preference for a clean area of a test chamber vs an area soiled by a conspecific. No differential responsiveness was found for a clean area as compared to an area soiled by either a sympatric species of garter snake (Thamnophis sirtalis) or by the individual water snake Ss. A similar series of tests with individual garter snakes (Thamnophis radix) revealed significant preferences for areas soiled either by the Ss themselves or by conspecifics as compared to clean areas. No preferences were found for a clean area of the test chamber vs an area soiled by a sympatric water snake (Natrix r. r.). The possible role of chemical cues in the mediation of dispersion and social responsiveness was discussed.     

Pretraining and discrimination reversal learning by rhesus monkeys

Groups of five to seven macaques were trained on repeated reversals of a visual (or spatial) discrimination habit after no pretraining, extended discrimination training, or repeated reversal training on spatial (or visual) cues. Neither sort of pretraining had a significant effect on reversal learning on the second cue. These results indicate that monkeys’ capacity to develop generalized “win-stay, lose-shift” hypotheses may have been exaggerated in previous experiments.     

Protein deprivation and food-related risk-taking preferences of rhesus monkeys

The relative preferences of four rhesus monkeys for reward probability versus reward amount when they were maintained on a low-protein (3.35%) diet were compared with those demonstrated when they were fed an adequate (13.4%) protein diet. Four stimulus objects, each signifying a different combination of reward frequency and amount (100%-one piece, 50%-2 pieces, 33%-three pieces, or 25%-four pieces), were presented in pairs, one pair per daily session, with trial schedules providing the same amount of reward within each set of 12 trials. Selections of the more frequently rewarded objects, but with lesser amounts per trial, were significantly higher during the low-protein phase than during either the preceding or the following normal-diet phases. Protein deprivation produces a changed motivational state making these animals less tolerant of infrequent or postponed reinforcement.     

Sample duration and type of stimuli in delayed matching-to-sample in rhesus monkeys

Two experiments were performed to determine the effect of sample duration (0.1, 2, and 4 sec), delay interval (.03, 4, 8, 16, and 32 sec), and type of stimulus (color and shape) on the matching performance of rhesus monkeys. In Experiment 1, the 15 possible delay-duration combinations were randomly presented in blocks of 15 trials. In Experiment 2, each duration was held constant and the five delays randomly presented. Then each delay interval was held constant with the three durations randomly varied. Matching performance increased as sample duration increased (ps < .01 and .005), while length of delay did not significantly affect performance. The type of stimuli paired in the matching test significantly affected performance (ps < .05 and .10) with the shape/shape choices leading to the poorest performance. Stimulus discriminability and amount of training with brief sample durations were implicated as significant determinants of matching performance.     

Feature-positive and feature-negative discrimination learning maintained by negative reinforcement in rhesus monkeys

Rhesus monkeys were trained to press panels to escape or avoid shock. Escape and avoidance training were combined factorially with feature-positive (FP) and feature-negative (FN) discriminations. In the FP situation, S+ trials were characterized by one red and two green panel displays and S? consisted of an all green panel array. In the FN arrangement, S+ and S? arrays were reversed. When compared properly, FP discriminations were learned more readily than FN discriminations in both escape and avoidance training conditions. Positive tracking was associated with FP discriminations, and feature avoidance characterized the FN tasks. These data suggest that in primates, feature responses (i.e., tracking behaviors) are more a function of the operant contingency than of the Pavlovian correlation.     

Learning of the insoluble conditional reaction problem by rhesus monkeys

Spiker’s modification of the Hull-Spence learning theory predicts that one particular type of conditional reaction problem is insoluble. However, a context-sensitive theory of discrimination learning developed by Medin predicts that this problem is soluble. Eight rhesus monkeys were trained on this previously uninvestigated problem for 36 days. Seven of the eight monkeys learned the problem, thus supporting the context-sensitive theory of discrimination learning.     

Visual discrimination learning of random figure problems by rhesus monkeys

In a two-choice discrimination learning paradigm, a U-shaped function was found between trials to criterion and the number of sides comprising the random figure discriminanda. These data are consistent with results from human Ss and suggest similar information processing capabilities in the two species. Changing the orientation of the stimulus figures after the discrimination had been learned only partially disrupted subsequent discrimination performance. Any single difference in selected form attributes between the two figures comprising a problem was not a good predictor of learning speed, suggesting that monkeys use a combination of such factors.     

Performance of rhesus monkeys on two-cue problems with cues separated

Relative performance on color and form dimensions during acquisition of two-cue problems by learning-set-sophisticated rhesus monkeys was evaluated with differential reinforcement. Six animals received 24 two-choice problems, each generated from three planometric stimuli, a reference stimulus, an alternate stimulus identical in color but differing in form, and one identical in form but differing in color. The reference stimulus appeared on every trial of a problem and was paired with one or the other alternate on a given trial On half of the problems, the reference stimulus was positive and on the remainder was negative. Acquisition was nearly equivalent on both cue dimensions with positive reference stimuli, but only one dimension was learned with negative reference stimuli. Results were interpreted as unfavorable to attention theory.     

Mother-infant interaction in rhesus monkeys treated clinically with delta-9-tetrahydrocannabinol

Behavior was studied in 15 rhesus monkeys mother-infant pairs, 5 of whom were exposed to delta-9-tetrahydrocannabinol continuously throughout gestation and the nursing period via drug treatment of mother (2.4 mg/kg/day). The drug-exposed mother-infant pairs were similar to nontreated controls in the amount and types displayed at 10 and 90 days of age, and adequate maternal care was demonstrated by all mothers. Drug-exposed pairs, however, showed no increase in interaction patterns that signal the onset of mother-infant independence at about 3 months of age. This finding suggests that mother-infant attachment may be a behavioral system that is particularly sensitive to modification by perinatal exposure to psychoactive drugs.     

Preference effects on acquisition and retention of concurrent discriminations by rhesus monkeys

Ten rhesus monkeys were trained on five tasks, each of which consisted of eight concurrently presented object discrimination problems. Sequences of presentation were devised to allow one, two, or three new tasks to intervene between acquisition and retention tests or to provide a 30-day period of no testing. Equivalent and proficient performances were obtained in all retention tests, and no relationship was observed between retention and the initial preference characteristics of various objects. Object pReferences did produce significant influences upon acquisition, but these effects were not as pronounced in early tasks as in later ones. An additional retention test provided support for the contention that monkeys do not necessarily process information about specific object pair discriminations. Rather, they appeared to retain a list of previously rewarded objects even when object pairings were different from those provided during acquisition. Concurrent discriminations involving many distinct objects were resistant to interference and independent of preference characteristics over long retention periods.     

Auditory matching-to-sample in monkeys (Cebus apella)

Four of 8 monkeys were successfully trained on an identity matching-to-sample task employing two acoustic stimuli. In five subsequent tests with different pairs of auditory stimuli, their performances were at levels that provided strong evidence for concept-mediated transfer. Thus, despite past failures to demonstrate the matching concept in the auditory modality, the present results indicate that the matching concept is not limited in monkeys to the visual modality. On the other hand, the failure of 4 subjects to learn the initial matching task constitutes additional evidence of cognitive asymmetry in monkeys with regard to the visual and auditory modalities.