Property in nonhuman primates

Property is rare in most nonhuman primates, most likely because their lifestyles are not conducive to it. Nonetheless, just because these species do not frequently maintain property does not mean that they lack the propensity to do so. Primates show respect for possession, as well as behaviors related to property, such as irrational decision making regarding property (e.g., the endowment effect) and barter. The limiting factor in species other than humans is likely the lack of social and institutional controls for maintaining property. By comparing primates and humans, we gain a better understanding of how human property concepts have evolved.     

Theory of mind in nonhuman primates

Since the BBS article in which Premack and Woodruff (1978) asked "Does the chimpanzee have a theory of mind?," it has been repeatedly claimed that there is observational and experimental evidence that apes have mental state concepts, such as "want" and "know." Unlike research on the development of theory of mind in childhood, however, no substantial progress has been made through this work with nonhuman primates. A survey of empirical studies of imitation, self-recognition, social relationships, deception, role-taking, and perspective-taking suggests that in every case where nonhuman primate behavior has been interpreted as a sign of theory of mind, it could instead have occurred by chance or as a product of nonmentalistic processes such as associative learning or inferences based on nonmental categories. Arguments to the effect that, in spite of this, the theory of mind hypothesis should be accepted because it is more parsimonious than alternatives or because it is supported by convergent evidence are not compelling. Such arguments are based on unsupportable assumptions about the role of parsimony in science and either ignore the requirement that convergent evidence proceed from independent assumptions, or fail to show that it supports the theory of mind hypothesis over nonmentalist alternatives. Progress in research on theory of mind requires experimental procedures that can distinguish the theory of mind hypothesis from nonmentalist alternatives. A procedure that may have this potential is proposed. It uses conditional discrimination training and transfer tests to determine whether chimpanzees have the concept "see." Commentators are invited to identify flaws in the procedure and to suggest alternatives.     

A two-way shuttlebox for testing nonhuman primates

The construction of a two-way shuttlebox suitable for testing nonhuman primates, such as rhesus macaques, is described. Special mention is made of those aspects of design and construction necessary to prevent subjects from solving experimental tasks in unforeseen and unwanted ways.     

Evolutionary developmental psychology: Contributions from comparative research with nonhuman primates

Evolutionary developmental psychology is a discipline that has the potential to integrate conceptual approaches to the study of behavioral development derived from psychology and biology as well as empirical data from humans and animals. Comparative research with animals, and especially with nonhuman primates, can provide evidence of adaptation in human psychological and behavioral traits by highlighting possible analogies (i.e., similar function, but independent evolution) or homologies (i.e., inheritance from a common ancestor) between human traits and similar traits present in animals. Data from nonhuman primates have played a crucial role in our understanding of infant attachment to the caregiver as a developmental adaptation for survival. Primate and human data are also consistent in suggesting that female interest in infants during the juvenile years may be a developmental adaptation for reproduction that facilitates the acquisition of maternal skills prior to the onset of reproduction.     

On inequity aversion in nonhuman primates

P. G. Roma, A. Silberberg, A. M. Ruggiero, and S. J. Suomi (2006) noted that the results S. F. Brosnan and F. B. M. de Waal (2003) attributed to inequity aversion could also be explained as a frustration effect. Roma et al. redressed this confound by designing a procedure that could have supported either of these interpretations. Nevertheless, they found that only a frustration effect accounted for both their data and those of Brosnan and de Waal (2003). The criticisms Brosnan and de Waal (2006) offered of Roma et al. ignored the fact that Brosnan and de Waal's (2003) research design was not capable of offering an unequivocal demonstration of inequity aversion. This conclusion holds no matter what the claimed inadequacies of Roma et al.'s procedures might have been. Caution is urged in inferring the existence of inequity aversion in nonhuman primates.     

Primacy and recency effects in nonhuman primates.

The reports of primacy and recency memory effects in nonhuman primates have been criticized because they have all used an initiating response. That is, the presentation of the to-be-remembered list of items was always contingent on a response being initiated by the nonhuman primate. It has been argued that this initiating response improves performance for early items in the list, resulting in the occurrence of the primacy effect, independent of any memory processing mechanism. This criticism was addressed in the present study by not using an initiating response prior to the presentation of the list. Nevertheless, both a primacy and a recency effect were observed in all 6 rhesus monkeys evaluated using a serial probe recognition task. Thus, the results are similar to those for humans, in that both primacy and recency effects can be obtained in nonhuman primates. A brief literature review is included, and it is proposed that the primacy and recency effects observed in humans, nonhuman primates, and infraprimates can be explained within the context of the configural-association theory.     

Irrational choice behavior in human and nonhuman primates

Choice behavior in humans has motivated a large body of research with a focus on whether decisions can be considered to be rational. In general, humans prefer having choice, as do a number of other species that have been tested, even though having increased choice does not necessarily yield a positive outcome. Humans have been found to choose an option more often only because the opportunity to select it was diminishing, an example of a deviation from economic rationality. Here we extend this paradigm to nonhuman primates in an effort to understand the mechanisms underlying this finding. In this study, we presented two groups of laboratory monkeys, capuchins (Cebus apella) and rhesus macaques (Macaca mulatta), as well as human subjects, with a computerized task in which subjects were presented with two differently colored icons. When the subject selected an icon, differing numbers of food pellets were dispensed (or points were assigned), making each icon correspond to a certain level of risk (one icon yielded 1 or 4 pellets/points and the other yielded 2 or 3). Initially, both options remained constantly available and we established choice preference scores for each subject. Then, we assessed preference patterns once the options were not continuously available. Specifically, choosing one icon would cause the other to shrink in size on the screen and eventually disappear if never selected. Selecting it would restore it to its full size. As predicted, humans shifted their risk preferences in the diminishing options phase, choosing to click on both icons more equally in order to keep both options available. At the group level, capuchin monkeys showed this pattern as well, but there was a great deal of individual variability in both capuchins and macaques. The present work suggests that there is some degree of continuity between human and nonhuman primates in the desire to have choice simply for the sake of having choice.     

A procedure for implanting chronic indwelling intraarterial catheters in nonhuman primates

A procedure for catheterizing the external iliac artery in nonhuman primates is described. This preparation can be used both for collecting blood samples and for infusing drugs. The preparation is well suited to long-term studies. Our experience indicates that, with appropriate maintenance, these catheters may remain patent for intervals of approximately 12 months.     

The organization of conspecific face space in nonhuman primates

Humans and chimpanzees demonstrate numerous cognitive specializations for processing faces, but comparative studies with monkeys suggest that these may be the result of recent evolutionary adaptations. The present study utilized the novel approach of face space, a powerful theoretical framework used to understand the representation of face identity in humans, to further explore species differences in face processing. According to the theory, faces are represented by vectors in a multidimensional space, the centre of which is defined by an average face. Each dimension codes features important for describing a face's identity, and vector length codes the feature's distinctiveness. Chimpanzees and rhesus monkeys discriminated male and female conspecifics’ faces, rated by humans for their distinctiveness, using a computerized task. Multidimensional scaling analyses showed that the organization of face space was similar between humans and chimpanzees. Distinctive faces had the longest vectors and were the easiest for chimpanzees to discriminate. In contrast, distinctiveness did not correlate with the performance of rhesus monkeys. The feature dimensions for each species’ face space were visualized and described using morphing techniques. These results confirm species differences in the perceptual representation of conspecific faces, which are discussed within an evolutionary framework.     

Sex-specific differences in olfactory sensitivity for putative human pheromones in nonhuman primates

In humans, the volatile C19-steroids androsta-4,16-dien-3-one (AND) and estra-1,3,5(10),16-tetraen-3-ol (EST) have been shown to modulate autonomic nervous system responses, and to cause hypothalamic activation in a gender-specific manner. Using two conditioning paradigms, the authors here show that pigtail macaques and squirrel monkeys of both sexes were able to detect AND and EST at concentrations in the micromolar and mM range, respectively. Male and female spider monkeys, in contrast, differed markedly in their sensitivity to these two odorous steroids, with males not showing any behavioral responses to the highest concentrations of AND tested and females not responding to the highest concentrations of EST. These data provide the first examples of sex-specific bimodal distributions of olfactory sensitivity in a nonhuman primate species.     

A simple and inexpensive method to measure urinary excretion in nonhuman primates

A simple and inexpensive automated method is described for simultaneous recording of time of day and frequency of urinary excretion. A 24-h event record for eight rhesus monkeys illustrates possible usefulness of the method in determining individual differences, response to environmental factors, and diumal patterns.     

Catheterization of the lumbar subarachnoid space for long-term CSF collection in unanesthetized nonhuman primates

Chronic indwelling spinal catheters facilitate administration of drugs and serial sampling of cerebrospinal fluid (CSF). Most catheters used in primates enter the ventricles or rostral subarachnoid space. This paper describes a procedure for catheterizing the lumbar subarachnoid space. Although the technique is invasive, maintenance and utilization of the catheter do not disturb the subject. The preparation remains patent for up to 21 days and permits both intrathecal drug administration and collection of CSF samples from unanesthetized subjects.     

The communicative functions of touch in humans, nonhuman primates, and rats: a review and synthesis of the empirical research

Although touch is one of the most neglected modalities of communication, several lines of research bear on the important communicative functions served by the modality. The authors highlighted the importance of touch by reviewing and synthesizing the literatures pertaining to the communicative functions served by touch among humans, nonhuman primates, and rats. In humans, the authors focused on the role that touch plays in emotional communication, attachment, bonding, compliance, power, intimacy, hedonics, and liking. In nonhuman primates, the authors examined the relations among touch and status, stress, reconciliation, sexual relations, and attachment. In rats, the authors focused on the role that touch plays in emotion, learning and memory, novelty seeking, stress, and attachment. The authors also highlighted the potential phylogenetic and ontogenetic continuities and discussed suggestions for future research.     

Manual laterality in nonhuman primates: a distinction between handedness and manual specialization

This article examines individual and group manual lateralization in nonhuman primates as a function of task's demands. It is suggested to distinguish low- from high-level manual activities with respect to the novelty variable and to the spatiotemporal scale of the movements. This review shows that low-level tasks lead to (a) symmetrical distributions of hand biases for the group and (b) manual preferences that are not indicative of the specialization of the contralateral hemisphere. In contrast, behaviors expressed in high-level tasks (a) show asymmetrical distribution of hand biases for the group and (b) seem to be related to a specialization of the contralateral hemisphere. Two types of lateralization, handedness and manual specialization, correspond to the 2 levels of tasks that are distinguished.     

Stimulus similarity and order as factors in visual short-term memory in nonhuman primates.

The short-term retention of nonhuman primates for a single sample or for two successively presented samples was assessed in four delayed matching-to-sample experiments with delays of .03, 4, 8, 16, and 32 sec. The single sample tasks included one (Experiment 1) or two (Experiment 4) distractor stimuli in the choice set (matching test). In the two successive samples tasks, the animals matched (reconstructed) the order of presentation of two samples with (Experiment 3) and without (Experiment 2) a distractor stimulus. Also, the possible combinations of eight stimuli (four colors and four shapes) were arranged to test the effects of sample set and choice set similarity. Taken together, analyses of the errors indicated that both sample and choice set similarity were significant sources of confusions in delayed matching. Order errors occurred independently of similarity but were a source of forgetting primarily at the longest delays (16 and 32 sec). Two exceptions to the similarity effect (second response errors in Experiment 3 and errors of an inexperienced group in Experiment 4) were observed. Possible reasons for the exceptions and several implications of these findings for theories of short-term memory are discussed.     

Displacement activities as a behavioral measure of stress in nonhuman primates and human subjects

Traditionally, research on human stress has relied mostly on physiological and psychological measures with a relatively minor emphasis on the behavioral aspects of the phenomenon. Such an approach makes it difficult to develop valid animal models of the human stress syndrome. A promising approach to the study of the behavioral correlates of stress is to analyze those behavior patterns that ethologists have named displacement activities and that, in primates, consist mostly of self-directed behaviors. In both nonhuman primates and human subjects, displacement behavior appears in situations characterized by social tension and is likely to reflect increased autonomic arousal. Pharmacological studies of nonhuman primates have shown that the frequency of occurrence of displacement behavior is increased by anxiogenic compounds and decreased by anxiolytic drugs. Ethological studies of healthy persons and psychiatric patients during interviews have found that increased displacement behavior not only correlates with a subjective feeling state of anxiety and negative affect but also gives more veridical information about the subject's emotional state than verbal statements and facial expression. The measurement of displacement activities may be a useful complement to the physiological and psychological studies aimed at analyzing the correlates and consequences of stress.     

Quantifying the face inversion effect in nonhuman primates: a phylogenetic meta-analysis

Animal Cognition - Face recognition is important for primate social cognition, enabling rapid discrimination between faces and objects. In humans, face recognition is characterized by certain...     

A Serial Reaction Time (SRT) task with symmetrical joystick responding for nonhuman primates

The serial reaction time (SRT) task is a simple procedure in which participants produce differentiated responses to each of a series of stimuli presented at varying locations. Learning about stimulus order is revealed through decreased latencies for structured versus randomized sequences. Although widely used with humans and well suited to nonhumans, this paradigm is little used in comparative research. In the present article, we describe an SRT procedure that uses colored circles as stimuli, a circular layout of locations, and symmetrical joystick deflections as responses. In two experiments, we showed that four rhesus macaques (Macaca mulatta) learned to track sequences up to eight items long, with three animals showing faster responding to repeating sequences than to randomized versions. After extended training, these participants also showed evidence of faster responding at all positions within repeating sequences. This method minimizes response effort, equates effort and travel distance across stimulus locations, and is applicable to any joystick-capable species.     

“Counting” serially presented stimuli by human and nonhuman primates and pigeons

Much of Stewart Hulse's career was spent analyzing how animals can extract patterned information from sequences of stimuli. Yet an additional form of information contained in a sequence may be the number of times different elements occurred. Experiments that required numerical discrimination between different stimulus items presented in sequence are analyzed for primates and pigeons. It is shown that a model based on magnitude discrimination can account well for data from human and nonhuman primate experiments. Similar experiments carried out with pigeons showed a strong recency effect not found with primates. The pigeon data are modeled successfully, however, by assuming that representations of events decay as other events are presented.