Choosing and Using Tools: Capuchins (Cebus apella) Use a Different Metric Than Tamarins (Saguinus oedipus).

Cotton-top tamarins (Saguinus oedipus) selected canes positioned so that a straight inward pull brought food within reach (M. D. Hauser, 1997; see also record 1997-41347-003). Tamarins failed to retrieve food with canes in other positions, and they did not reposition these canes. In this study, tufted capuchin monkeys (Cebus apella) preferred canes they could pull straight in when these were present, but they also repositioned canes in individually variable ways, and their success at obtaining food with repositioned canes improved with practice. In accord with predictions drawn from ecological psychology, capuchins discovered affordances of canes through exploratory actions with these objects, whereas tamarins did not. Ecological theory predicts these differences on the basis of species-typical manipulative activity, and it provides a useful approach for the study of species differences in tool-using behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

What guides a search for food that has disappeared? Experiments on cotton-top tamarins (Saguinus oedipus).

When food is launched down a vertically positioned S-shaped opaque tube, cotton-top tamarins (Saguinus oedipus) search for the food in the position directly beneath the release point, even though over several trials it never appears in this position (B. M. Hood et al., 1999). Experiment 1 showed that when the trajectory of the food shifts from the vertical to the horizontal plane, tamarins no longer show systematic perseverative errors and, in general, perform better on this invisible displacement task. Experiment 2 showed that tamarins with experience on the horizontal task show less of a bias when tested on the vertical task but nonetheless fail overall to solve this invisible displacement problem; their performance is substantially worse than it was on the horizontal task. Experiment 3 revealed that when the vertically positioned tube is replaced by an occluded ramp, tamarins consistently search in the compartment below the release point, even though most of the tamarins had experience in Experiments 1 and 2. Overall, results indicate that tamarins have a significant gravity bias when searching for food that has disappeared along the vertical plane but also have more general problems finding food that has moved out of sight. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Spatial cues more salient than color cues in cotton-top tamarins (Saguinus oedipus) reversal learning.

Animals living in stable home ranges have many potential cues to locate food. Spatial and color cues are important for wild Callitrichids (marmosets and tamarins). Field studies have assigned the highest priority to distal spatial cues for determining the location of food resources with color cues serving as a secondary cue to assess relative ripeness, once a food source is located. We tested two hypotheses with captive cotton-top tamarins: (a) Tamarins will demonstrate higher rates of initial learning when rewarded for attending to spatial cues versus color cues. (b) Tamarins will show higher rates of correct responses when transferred from color cues to spatial cues than from spatial cues to color cues. The results supported both hypotheses. Tamarins rewarded based on spatial location made significantly more correct choices and fewer errors than tamarins rewarded based on color cues during initial learning. Furthermore, tamarins trained on color cues showed significantly increased correct responses and decreased errors when cues were reversed to reward spatial cues. Subsequent reversal to color cues induced a regression in performance. For tamarins spatial cues appear more salient than color cues in a foraging task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cooperatively breeding cottontop tamarins (Saguinus oedipus) do not donate rewards to their long-term mates.

This study tested the hypothesis that cooperative breeding facilitates the emergence of prosocial behavior by presenting cottontop tamarins (Saguinus oedipus) with the option to provide food rewards to pair-bonded mates. In Experiment 1, tamarins could provide rewards to mates at no additional cost while obtaining rewards for themselves. Contrary to the hypothesis, tamarins did not demonstrate a preference to donate rewards, behaving similar to chimpanzees in previous studies. In Experiment 2, the authors eliminated rewards for the donor for a stricter test of prosocial behavior, while reducing separation distress and food preoccupation. Again, the authors found no evidence for a donation preference. Furthermore, tamarins were significantly less likely to deliver rewards to mates when the mate displayed interest in the reward. The results of this study contrast with those recently reported for cooperatively breeding common marmosets, and indicate that prosocial preferences in a food donation task do not emerge in all cooperative breeders. In previous studies, cottontop tamarins have cooperated and reciprocated to obtain food rewards; the current findings sharpen understanding of the boundaries of cottontop tamarins’ food-provisioning behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Self-control and tool use in tufted capuchin monkeys (Cebus apella).

Self-control is defined as forgoing immediate gratification to obtain a greater reward. Tool use may relate to self-control because both behaviors may require foresight and deliberate control over one's actions. The authors assessed 20 capuchin monkeys (Cebus apella) for the ability to delay gratification in a tool task. Subjects were given rod-shaped food items that could either be consumed immediately or be carried to an apparatus and used to extract a more preferred food. The authors found that some monkeys were able to exhibit self-control. Monkeys with relatively more tool use experience demonstrated the greatest levels of self-control. These results indicate that capuchins are capable of delaying gratification when a higher quality reinforcer is present and that tool experience can influence levels of self-control in this task. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Is a sense of inequity an ancestral primate trait? Testing social inequity in cotton top tamarins (Saguinus oedipus).

To address a controversy in the literature concerning whether monkeys show an aversion to inequity, individuals of a New World monkey species, cotton top tamarins (Saguinus oedipus) were tested in an offering task and in a bartering task. At issue was whether the monkeys rejected rewards because of a violation of expectancy of the preferred reward, or whether they rejected rewards because of a sensitivity to socially mediated inequity. The data from both tasks indicated that the subjects were more likely to reject when preferred rewards were presented, either because of another animal eating the reward (the social condition) or because of rewards being presented but inaccessible. The bartering task led to the only behavioral indication of aversion due specifically to social inequity, which was demonstrated when tamarins' sensitivity to the difference in rewards increased with exposure to other tamarins working to receive the preferred rewards. The results suggest that social inequity aversion will be assessed by tamarins, and possibly by other primates, only under conditions of limited resources and a requirement of work, which may make the situation a bit more competitive and thus drives attention toward both social and reward evaluation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The relationship between problem solving and inhibitory control: Cotton-top tamarins ( Saguinus oedipus ) performance on a reversed contingency task.

To explore the relationship between problem solving and inhibitory control, the authors present 4 experiments on cotton-top tamarins (Saguinus oedipus) using a reverse-reward contingency task. In Experiment 1, 1 group of tamarins was given a choice between a small and a large quantity of food. Whichever quantity the tamarins reached for first, they received the alternative. The tamarins consistently picked the larger quantity, thereby receiving the smaller. A 2nd group of tamarins was given the same task, except that if they reached for the larger quantity of food, they received nothing. The tamarins continued to pick the larger quantity, even though this resulted in no food. In addition, most of the tamarins continued to pick the larger quantity even when the food payoff for choosing the smaller quantity was increased (Experiment 2) or when the visual salience of the food was reduced (Experiment 3). Experiment 4 was based on the finding that chimpanzees (Pan troglodytes) that have been trained on the concept of number can solve the reversed contingency task if the food is replaced by Arabic numerals. With the help of a color association, and a higher cost incurred by picking the color associated with 3 food items, the tamarins learned to pick the color associated with... (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The win-stay rule in foraging decisions by free-ranging titi monkeys (Callicebus cupreus cupreus) and tamarins (Saguinus imperator imperator and Saguinus fuscicollis weddelli).

Rainforest primates need to apply distinct foraging rules for efficiently using the spatial knowledge of the distribution of resources showing different temporal patterns of renewal. A win-stay rule is very important for exploiting abundant, long-lasting resources. Here, the author tests the use of this rule in wild groups of emperor tamarins (Saguinus imperator imperator), saddle-back tamarins (Saguinus fuscicollis weddelli), and titi monkeys (Callicebus cupreus cupreus) during a series of foraging tasks. Four feeding stations composed of 8 visually similar feeding platforms (2 containing a food reward and 6 containing a sham reward) were constructed. The location of food rewards was reliable during some experiments and unreliable during others. All 3 species consistently adopted a win-stay rule for returning to reward platforms when their location was predictable over time but stopped using it when their spatial distribution changed randomly across experimental trials. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cognitive preconditions for responses to fairness: An object retrieval test of inhibitory control in capuchin monkeys (Cebus apella).

The authors explore the evolution of one cognitive mechanism required for altruistic behavior: the capacity to inhibit prepotent responses. Specifically, the authors used an object retrieval task to investigate whether capuchins (Cebus apella) can inhibit a prepotent strategy of reaching directly for a food reward. Success in this task varies across species and across development, but is also known to depend critically on the maturity of dorsolateral prefrontal cortex, the cortical area implicated in rejecting small payoffs in an Ultimatum Game. Capuchins easily inhibit the tendency to reach directly for food in the object retrieval task, successfully employing an alternative reaching strategy even in the first session of performance. This contrasts with the performance of closely related tamarin monkeys, who performed less well despite extensive training. These results provide the first evidence that capuchins likely exhibit human-like inhibitory control in tasks previously linked to the function of the dorsolateral prefrontal cortex, such as the Ultimatum Game. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Capuchin monkeys, Cebus apella fail to understand a cooperative task

We investigated whether capuchin monkeys cooperate to solve a task and to what extent they take into account the behaviour of another individual when cooperating. Two groups of capuchin monkeys (N=5 and 6) were tested in a task whose solution required simultaneous pulling of two handles which were too far from one another to be pulled by one monkey. Before carrying out the cooperation study, individual monkeys were trained to pull one handle (training phase 1) and to pull two handles simultaneously (training phase 2) for a food reward. Nine subjects were successful in training phase 1, and five in training phase 2. In the cooperation study seven subjects were successful, that is, pulled one handle while a companion pulled the other. Further analyses revealed that capuchins did not increase their pulling actions when a partner was close to or at the other handle, that is, when cooperation might occur. These data suggest that capuchin monkeys acted together at the task and got the reward without understanding the role of the partner and without taking its behaviour into consideration. Social tolerance, as well as their tendency to explore and their manual dexterity, were the major factors accounting for the capuchins' success.Copyright 1997 The Association for the Study of Animal Behaviour1997The Association for the Study of Animal Behaviour     

How tree shrews (Tupaia belangeri) perform in a searching task: Evidence for strategy use.

This study investigated how male tree shrews (Tupaia balngeri) performed in a searching task while in their home cages and assessed whether different food distributions affected their performance. The animals were faced with a holeboard containing 9 food sources arranged in a 3 X 3 matrix or in 3 clusters, each containing 3 sources. Animals tended to start and end the trials from preferred locations, thereafter solving the task by strategically organizing the reward collection according to a minimum-distance principle. In the cluster configuration, they visited the sources hierarchically. Food distribution did not affect the performance. Comparison with data from mice and capuchin monkeys revealed that tree shrews and capuchins solved the task in a similar strategic way, whereas mice did not. These findings attract particular attention because of the phylogenetic position of tree shrews, which are regarded as closely related to primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inhibitory Control and Response Selection in Problem Solving: How Cotton-Top Tamarins (Saguinus oedipus) Overcome a Bias for Selecting the Larger Quantity of Food.

When presented with a choice between 1 and 3 pieces of food in a type of reversed contingency task, 4 cotton-top tamarins (Saguinus oedipus) consistently chose the 3 pieces of food and received nothing, even though the choice of 1 piece would have yielded 3. However, in a task in which the tamarins received the 1 piece of food when they chose it, all subjects learned to select 1 over 3. Thus, the tamarins' prior failure on the reversed contingency task did not result entirely from an inherent inability to suppress the prepotent response of reaching to the larger of 2 quantities of food. After the experience of selecting the smaller quantity and receiving it, all of the tamarins solved the version of the reversed contingency task that they failed initially. These results suggest that the tamarins' initial failure may have reflected a difficulty with selecting an alternative response option. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Socially Learned Preferences for Differentially Rewarded Tokens in the Brown Capuchin Monkey (Cebus apella).

Social learning is assumed to underlie traditions, yet evidence indicating social learning in capuchin monkeys (Cebus apella), which exhibit traditions, is sparse. The authors tested capuchins for their ability to learn the value of novel tokens using a previously familiar token-exchange economy. Capuchins change their preferences in favor of a token worth a high-value food reward after watching a conspecific model exchange 2 differentially rewarded tokens, yet they fail to develop a similar preference after watching tokens paired with foods in the absence of a conspecific model. They also fail to learn that the value of familiar tokens has changed. Information about token value is available in all situations, but capuchins seem to pay more attention in a social situation involving novel tokens. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Artifactual kinds and functional design features: what a primate understands without language

Of several domains of knowledge, humans appear to be born with an innately structured representational system for making sense of objects, what properties individuate them, how they move in space, and what causes them to move from one location to another. They also appear to make simple conceptual cuts between artifactual kinds and living kinds. The basis for this distinction seems to be a combination of crucial functional properties, together with a teleological (i.e., historical/intentional) stance, one that asks 'What was this object designed for?'. Although non-human primates also appear to have considerable understanding of objects, and often use objects as tools, it is not clear whether they draw a distinction between artifactual and living kinds, and if so, what factors guide this distinction. As a step in addressing this problem, I present experiments on a small New World monkey, the cotton-top tamarin (Saguinus oedipus oedipus), designed to reveal their understanding of the functional properties of tools using a procedure associated with minimal training. Specifically, the experiments explored whether tamarins distinguish between relevant and irrelevant properties of a tool, and further, understand that some features can be transformed with little cost to functionality. The first experiment was a means-end task and involved using a cane-like object (a tool) to access a piece of food. In this experiment, there were always two choices: either the food was immediately accessible because it was located on the inside of the cane's hook or less readily accessible because it was located on the outside of the hook. Most of the tamarins reached criterion on this task within a few sessions, consistently picking the cane with the most accessible food. Subsequent experiments (2-4) involved property changes (i.e., its color, texture, size and shape) that had either significant or relatively insignificant effects on the tool's function. In general, the tamarins appeared tolerant of all property transformations as evidenced by the fact that they selected each object at least once. However, clear preferences also emerged suggesting that some properties had a more significant impact on the tool's functionality. Thus, in head-to-head competitions, tools with color or texture changes were selectively preferred over tools with shape or size changes. This makes sense color and texture do not effect the tool's function, whereas shape and size do. The final experiments involved both novel and familiar objects that, based on their current configuration, could readily be used as tools, in contrast with objects that required considerable manipulation to convert into a tool. Consistently, the tamarins preferred possible over convertible tools, and when two convertible tools were presented at the same time, they preferred the tool that required the fewest changes to the required motor response. Results suggest that the tamarins distinguish between relevant and irrelevant properties of a tool and this distinction is based on functionality, on having good design. This ability is especially surprising given the fact that tamarins do not naturally use tools, and infrequently come into contact with artifacts. Results are discussed in light of current theories concerning the representational foundations of natural kinds, and in particular, artifactual kinds.     

Genetic correlation between performance on an appetitive-signaled nosepoke task and voluntary ethanol consumption

The present study used a signaled appetitive nosepoke task as a measure of behavioral control or impulsivity related to reward system function in mice and determined how impulsivity correlated with voluntary ethanol consumption. Thirteen inbred strains were trained to nosepoke for food rewards and eventually trained to nosepoke for reward when an auditory signal was presented. Efficiency in the signaled nosepoke task indicated the ability of the mice to withhold the nosepoke response until the signal to respond for a reward was given and was considered indicative of behavioral control or impulsivity. After completion of the nosepoke task, the mice were tested for ethanol consumption in a three-bottle choice test at 3 and 10% (v/v) ethanol concentrations. Behavioral measures from the nosepoke task and ethanol consumption measures were correlated to determine a genetic relationship. High efficiency, the ability to withhold nosepoking until signaled, was negatively correlated with ethanol consumption. Thus, the strains who were better able to control their behavioral responding (i.e., less impulsive) consumed less ethanol, and strains who were more impulsive consumed more ethanol. This genetic relationship may be a mouse behavioral model for some of the neuropsychological traits demonstrated in human subjects who are family history-positive for alcoholism.     

Assessment of shoulder dimensions and angles of porcelain bonded to metal crown preparations

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.     

Tufted capuchin monkeys (Cebus apella) spontaneously use visual but not acoustic information to find hidden food items.

Foraging choices in tufted capuchins monkeys are guided by perceptual, cognitive, and motivational factors, but little is known about how these factors might interact. The present study investigates how different types of sensory information affect capuchins' ability to locate hidden food. In two experiments, capuchins were presented with two cups, one baited and one empty. Monkeys were given visual, acoustic, or acoustic-visual information related to the baited cup, the empty cup, or both baited and empty cup. Results show that capuchins spontaneously used visual information to locate food, and that information indicating presence and absence of food led to higher success rates than information indicating only absence of food. In contrast, acoustic information did not lead to success rates above chance levels and failed to enhance performance in combination with visual information. Capuchins spontaneously avoided a visually empty cup, but they did not appear to associate sounds with either the presence or absence of food. Being able to locate food items with the aid of acoustic cues might be a learned process that requires interactive experiences with the task's contingencies. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Gorillas (Gorilla gorilla) and Orangutans (Pongo pygmaeus) Encode Relevant Problem Features in a Tool-Using Task.

Two important elements in problem solving are the abilities to encode relevant task features and to combine multiple actions to achieve the goal. The authors investigated these 2 elements in a task in which gorillas (Gorilla gorilla) and orangutans (Pongo pygmaeus) had to use a tool to retrieve an out-of-reach reward. Subjects were able to select tools of an appropriate length to reach the reward even when the position of the reward and tools were not simultaneously visible. When presented with tools that were too short to retrieve the reward, subjects were more likely to refuse to use them than when tools were the appropriate length. Subjects were proficient at using tools in sequence to retrieve the reward. (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)     

Conserved Sp?tzle/Toll signaling in dorsoventral patterning of Xenopus embryos

Three Cynomolgus monkeys (Macaca fascicularis) learned a flavour-visual conditional discrimination problem, in which one of two possible food items was presented at the beginning of each trial, and acted as an instruction cue to signal which of two visually distinct stimulus objects the animal must displace on that trial in order to obtain a further food reward. The task was learned first in light then in dark conditions. Following rhinal cortex ablation the animals were unable to use the flavour properties of the food items to guide visual choices, performing at close to chance levels. Postoperative performance on a food preference test showed that their problem in associating a flavour cue with a visual object in the conditional learning task also extended to aberrant choice of foods based on their visual appearance.