Token mediated tool exchange between tufted capuchin monkeys (<Emphasis Type="Italic">Cebus apella</Emphasis>)

Three experiments were conducted to test whether a pair of tufted capuchin monkeys (Cebus apella) could generalize their ability to exchange tokens and tool objects with a human experimenter to similar exchanges with a conspecific partner. Monkeys were tested in side-by-side enclosures, one enclosure containing a tool-use apparatus and one or more token(s), and the other enclosure containing one or more tool object(s). The monkeys willingly transferred tokens and tools to a conspecific with little practice. Following a small amount of training, we also found that the monkeys would select situation-appropriate tokens to exchange for specific tools, but did not select appropriate tool objects in response to another monkey’s token transfers. Implications regarding role reversal are discussed.     

Transport of tools to food sites in tufted capuchin monkeys (<Emphasis Type="Italic">Cebus apella</Emphasis>)

Tool use and transport represent cognitively important aspects of early hominid evolution, and nonhuman primates are often used as models to examine the cognitive, ecological, morphological and social correlates of these behaviors in order to gain insights into the behavior of our early human ancestors. In 2001, Jalles-Filho et al. found that free-ranging capuchin monkeys failed to transport tools (stones) to food sites (nuts), but transported the foods to the tool sites. This result cast doubt on the usefulness of Cebus to model early human tool-using behavior. In this study, we examined the performance of six captive tufted capuchin monkeys (Cebus apella) in a tool transport task. Subjects were provided with the opportunity to transport two different tools to fixed food reward sites when the food reward was visible from the tool site and when the food reward was not visible from the tool site. We found that the subjects quickly and readily transported probing tools to an apparatus baited with syrup, but rarely transported stones to a nut-cracking apparatus. We suggest that the performance of the capuchins here reflects an efficient foraging strategy, in terms of energy return, among wild Cebus monkeys.     

Joystick acquisition in tufted capuchins (<Emphasis Type="Italic">Cebus apella</Emphasis>)

A number of nonhuman primate species have demonstrated the ability to use a joystick to control a cursor on a computer screen, yet the acquisition of this skill has not been the focus of systematic inquiry. Here, we examined joystick acquisition in four tufted capuchins under two directional relationships of joystick movement and resultant cursor displacement, isomorphic and inverted. To document the natural history of the acquisition of this skill, we recorded the development of visual tracking of the cursor and body tilting. Rates of acquisition were comparable between the two conditions. After mastering the task in one condition, subjects remastered the task at an accelerated rate in the opposing condition. All subjects significantly increased or maintained high proportions of cursor tracking throughout acquisition. All subjects demonstrated a postural tilt while moving the cursor from the mid-phase of acquisition through task mastery. In the isomorphic condition, all subjects tilted significantly more often in the direction of goal location than in the opposite direction. In three of the four series of tilting that were scored for subjects in the inverted condition, tilting occurred significantly more often toward the direction of goal location than the direction of required hand movement. Together these findings suggest that body tilting participates in the organization of directional movement of the cursor rather than reflecting merely the motoric requirements of the task (to manipulate a joystick).     

Tufted capuchins (<Emphasis Type="Italic">Cebus apella</Emphasis>) attribute value to foods and tools during voluntary exchanges with humans

This research examined exchange and value attribution in tufted capuchin monkeys (Cebus apella). We presented subjects with opportunities to obtain various foods and a tool from an experimenter in exchange for the foods or tool in the subjects' possession. The times elapsed before the first chow biscuits were expelled and/or an exchange took place were recorded as the dependent measures. Laboratory chow biscuits, grapes, apples, and a metal bolt (a tool used to probe for syrup) were used as experimental stimuli. The subjects demonstrated the ability to recognize that exchanges could occur when an experimenter was present with a desirable food. Results indicate that subjects exhibited significant variation in their willingness to barter based upon the types of foods that were both in their possession and presented by the experimenter. Subjects more readily traded chow biscuits for fruit, and more readily traded apples for grapes than grapes for apples. During the exchange of tools and food, the subjects preferred the following in descending order when the probing apparatus was baited with sweet syrup: grapes, metal bolts, and chow biscuits. However when the apparatus was not baited, the values changed to the following in descending order: grapes, chow, and metal bolts. These results indicate that tufted capuchins recognize opportunities to exchange and engage in a simple barter system whereby low-valued foods are readily traded for more highly valued food. Furthermore, these capuchins demonstrate that their value for a tool changes depending upon its utility.     

Experimental field study of hand preference in wild black-horned (<Emphasis Type="Italic">Cebus nigritus</Emphasis>) and white-faced (<Emphasis Type="Italic">Cebus capucinus</Emphasis>) capuchins: evidence for individual and species differences

In this experimental field investigation, we compare the degree to which wild capuchins in Brazil (Cebus nigritus) and Costa Rica (Cebus capucinus) exhibit individual- and population-level handedness during three visually-guided tasks. These tasks required reaching to remove a large leaf covering a hidden food reward, seizing the food reward, and manipulating a tool (pulling a wooden dowel) in order to obtain access to an embedded food reward. Studies in some populations of captive capuchins indicate evidence for both individual hand preferences and population-level handedness. In this study, six of eight wild C. capucinus and six of seven wild C. nigritus exhibited a significant hand preference during individual tasks, but no individual exhibited a consistent preference across all three tasks. Task-specialization, or the tendency for most individuals in the same group or population to use the same hand to accomplish a particular task, also was evaluated. Cebus nigritus showed a significant bias toward the use of the right hand in removing the leaf. Although the number of individual capuchins in both species that manipulated the dowels was limited (N = 7), each individual that manipulated the dowels in eight or more instances had a positive handedness index, suggesting a greater use of the right hand to accomplish this task. Overall, our results provide preliminary support for individual- and population-level handedness in wild capuchin monkeys.     

Observational learning from tool using models by human-reared and mother-reared capuchin monkeys (<Emphasis Type="Italic">Cebus apella</Emphasis>)

Studies of wild capuchins suggest an important role for social learning, but experiments with captive subjects have generally not supported this. Here we report social learning in two quite different populations of capuchin monkeys (Cebus apella). In experiment 1, human-raised monkeys observed a familiar human model open a foraging box using a tool in one of two alternative ways: levering versus poking. In experiment 2, mother-raised monkeys viewed similar techniques demonstrated by monkey models. A control group in each population saw no model. In both experiments, independent coders detected which technique experimental subjects had seen, thus confirming social learning. Further analyses examined fidelity of copying at three levels of resolution. The human-raised monkeys exhibited fidelity at the highest level, the specific tool use technique witnessed. The lever technique was seen only in monkeys exposed to a levering model, by contrast with controls and those witnessing poke. Mother-reared monkeys instead typically ignored the tool and exhibited fidelity at a lower level, tending only to re-create whichever result the model had achieved by either levering or poking. Nevertheless this level of social learning was associated with significantly greater levels of success in monkeys witnessing a model than in controls, an effect absent in the human-reared population. Results in both populations are consistent with a process of canalization of the repertoire in the direction of the approach witnessed, producing a narrower, socially shaped behavioural profile than among controls who saw no model. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Tool-use in a display behaviour by Eurasian beavers (<Emphasis Type="Italic">Castor fiber</Emphasis>)

Tool use is rare amongst rodents and has never been recorded in connection with agonistic displays. We witnessed a behaviour, stick display (StD), involving tool use in free-living Eurasian beavers (Castor fiber) that we conclude is a display behaviour. Two beavers were the main performers of the signal that was observed in at least six beavers from three families. Beavers reacted to displays by increased evasive and agonistic behaviours compared with their usual behavioural patterns when at territory borders. The behaviour was almost exclusively seen between rivals at territory borders. We suggest that the display is used in agonistic encounters, mainly in a territorial context. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

<Emphasis Type="Italic">Ziran</Emphasis> and <Emphasis Type="Italic">Wuwei</Emphasis> in the <Emphasis Type="Italic">Daodejing</Emphasis>: An Ethical Assessment

In Daoist philosophy, the self is understood as an individual interdependent with others, and situated within a broader environment. Within this framework, the concept ziran is frequently understood in terms of naturalness or nature while wuwei is explained in terms of non-oppressive government. In many existing accounts, little is done to connect these two key Daoist concepts. Here, I suggest that wuwei and ziran are correlated, ethical, concepts. Together, they provide a unifying ethical framework for understanding the philosophy of the Daodejing. I explore the meaning of ziran as self-so-ness or, in human terms, as pertaining to an individual’s spontaneity. The appropriate response to the spontaneity of individuals is to avoid, insofar as possible, imposing or using restrictive norms and methods, that is, wuwei. According to this view, ziran and wuwei offer an account of ethics that attends to core notions of interdependent selfhood, including mutuality, relationality, interdependence, symbiosis, and responsiveness.     

Comparing responses to novel objects in wild baboons (<Emphasis Type="Italic">Papio ursinus</Emphasis>) and geladas (<Emphasis Type="Italic">Theropithecus gelada</Emphasis>)

Behavioral flexibility is considered by some to be one of the hallmarks of advanced cognitive ability. One measure of behavioral flexibility is how subjects respond to novel objects. Despite growing interest in comparative cognition, no comparative research on neophilia in wild primates has been conducted. Here, we compare responses to novel objects in wild chacma baboons (Papio ursinus) and geladas (Theropithecus gelada). Baboons and geladas are closely related taxa, yet they differ in their ecology and degree of social tolerance: (1) baboons are habitat and dietary generalists, whereas geladas have one of the most specialized primate diets (90% grass); (2) baboons exhibit an aversion toward extra-group individuals, whereas geladas typically exhibit an attraction toward them. Using subjects of all age and sex classes, we examined responses to three different objects: a plastic doll, a rubber ball, and a metal can. Overall, baboon subjects exhibited stronger responses to the objects (greater neophilia and exploration) than gelada subjects, yet we found no evidence that the geladas were afraid of the objects. Furthermore, baboons interacted with the objects in the same way they might interact with a potential food item. Responses were unrelated to sex, but immatures showed more object exploration than adults. Results corroborate novel object research conducted in captive populations and suggest that baboons and geladas have differences in behavioral flexibility (at least in this cognitive domain) that have been shaped by ecological (rather than social) differences between the two species. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Three-Valued Temporal Logic <Emphasis Type="Italic">Q</Emphasis><Subscript><Emphasis Type="Italic">t</Emphasis></Subscript> and Future Contingents

Prior’s three-valued modal logic Q was developed as a philosophically interesting modal logic. Thus, we should be able to modify Q as a temporal logic. Although a temporal version of Q was suggested by Prior, the subject has not been fully explored in the literature. In this paper, we develop a three-valued temporal logic Q _t and give its axiomatization and semantics. We also argue that Q _t provides a smooth solution to the problem of future contingents. Presented by Daniele Mundici     

Food and token quantity discrimination in capuchin monkeys (<Emphasis Type="Italic">Cebus apella</Emphasis>)

Quantity discrimination is adaptive in a variety of ecological contexts and different taxa discriminate stimuli differing in numerousness, both in the wild and in laboratory settings. Quantity discrimination between object arrays has been suggested to be more demanding than between food arrays but, to our knowledge, the same paradigm has never been used to directly compare them. We investigated to what extent capuchin monkeys’ relative numerousness judgments (RNJs) with food and token are alike. Tokens are inherently non-valuable objects that acquire an associative value upon exchange with the experimenter. Our aims were (1) to assess capuchins’ RNJs with food (Experiment 1) and with tokens (Experiment 2) by presenting all the possible pair-wise choices between one to five items, and (2) to evaluate on which of the two proposed non-verbal mechanisms underlying quantity discrimination (analogue magnitude and object file system) capuchins relied upon. In both conditions capuchins reliably selected the larger amount of items, although their performance was higher with food than with tokens. The influence of the ratio between arrays on performance indicates that capuchins relied on the same system for numerical representation, namely analogue magnitude, regardless of the type of stimuli (food or tokens) and across both the small and large number ranges.     

Capuchins (<Emphasis Type="Italic">Cebus apella</Emphasis>) fail to show an asymmetric dominance effect

The asymmetric dominance effect (ADE) occurs when the introduction of a partially dominated decoy option increases the choice share of its dominating alternative. The ADE is a violation of regularity and the constant-ratio rule, which are two derivations of the independence of irrelevant alternatives axiom, a core tenant of rational choice. The ADE is one of the most widely reported human choice phenomena, leading researchers to probe its origins by studying a variety of non-human species. We examined the ADE in brown capuchin monkeys (Cebus apella), a species that displays many other decision biases. In Experiment 1, we used a touchscreen method to elicit choice-based preferences for food rewards in asymmetrically dominated choice sets. In Experiments 2 and 3, we distinguished between different types of judgments and used a free selection task to elicit consumption-based preferences for juice rewards. However, we found no evidence for the ADE through violations of regularity or the constant-ratio rule, despite the similarity of our stimuli to other human and non-human experiments. While these results appear to conflict with existing literature on the ADE in non-human species, we point out methodological differences—notably, the distinction between value-based and perception-based stimuli—that have led to a collection of phenomena that are difficult to understand under a unitary theoretical framework. In particular, we highlight key differences between the human and non-human research and provide a series of steps that researchers could take to better understand the ADE.     

Representations of monadic <Emphasis Type="Italic">MV</Emphasis> -algebras

Representations of monadic MV -algebra, the characterization of locally finite monadic MV -algebras, with axiomatization of them, definability of non-trivial monadic operators on finitely generated free MV -algebras are given. Moreover, it is shown that finitely generated m-relatively complete subalgebra of finitely generated free MV -algebra is projective.     

Combinations of <Emphasis Type="Italic">Stit</Emphasis> with <Emphasis Type="Italic">Ought</Emphasis> and <Emphasis Type="Italic">Know</Emphasis>

This paper presents a short survey of recent developments in stit theories, with an emphasis on combinations of stit and deontic logic, and those of stit and epistemic logic.     

Learning generalization in problem solving by a blue-fronted parrot (<Emphasis Type="Italic">Amazona aestiva</Emphasis>)

Pepperberg (The Alex studies: cognitive and communicative abilities of gray parrots. Harvard University Press, Cambridge;1999) showed that some of the complex cognitive capabilities found in primates are also present in psittacine birds. Through the replication of an experiment performed with cotton-top tamarins (Saguinus oedipus oedipus) by Hauser et al. (Anim Behav 57:565-582; 1999), we examined a blue-fronted parrot's (Amazona aestiva) ability to generalize the solution of a particular problem in new but similar cases. Our results show that, at least when it comes to solving this particular problem, our parrot subject exhibited learning generalization capabilities resembling the tamarins'.     

Discrimination of contour-deleted images in baboons (<Emphasis Type="Italic">Papio papio</Emphasis>) and chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

Humans readily group component elements into a coherent perceptual whole and perceive the global form of visual patterns in priority over local features, which stands in contrast to at least some data from the animal literature, suggesting possible species differences in perceptual processes. In this study, chimpanzees and baboons were required to match intact and partially contour-deleted line-drawings in a computerized task in order to further explore the ability of nonhuman primates to group component elements into a coherent perceptual whole and to determine to what extent they use the global form or the local features. Experiment 1 showed that the baboons and chimpanzees matched intact continuous line-drawings (intact-intact) more easily than partially contour-deleted line-drawings (deleted-deleted). Both species could also match partially deleted line-drawings with their intact version (deleted-intact), but at a lower performance level. Experiment 2 further showed that subjects from the two species could match partially deleted coherent line-drawings (deleted-deleted) more easily than their scrambled incoherent versions (scrambled-scrambled). They could however match the coherent deleted forms with their scrambled version (deleted-scrambled). It is suggested that solutions of these tasks rely on the processing of both global and local cues, with no clear-cut species difference in that ability. Overall, the results show that contour completion of line-drawings was not easy. Implications on the processing of human-made two-dimensional representations such as line-drawings are discussed.     

Sign- and goal-tracking in Atlantic cod (<Emphasis Type="Italic">Gadus morhua</Emphasis>)

When animals associate a stimulus with food, they may either direct their response towards the stimulus (sign-tracking) or towards the food (goal-tracking). The direction of the conditioned response of cod was investigated to elucidate how cod read cue signals. Groups of cod were conditioned to associate a blinking light (conditioned stimulus, CS) with a food reward (unconditioned stimulus, US), with the CS and the US located at opposite sides of the tank. Two groups were trained in a delay conditioning procedure (CS = 60 s, interstimulus interval = 30 s) and two groups were trained in a trace conditioning procedure (CS = 12 s, trace interval = 20 s). The response pattern was similar for the delay- and trace-conditioned groups. The initial main response at the onset of the CS was approaching the blinking lights, i.e. sign-tracking. In the early trials, the fish did not gather in the feeding area before the arrival of food. In the later trials, the fish first approached the blinking lights, but then moved across the tank and gathered below the feeder before the food arrived, i.e. sign-tracking followed by goal-tracking within each trial. These two responses are interpreted as reflecting two learning systems, i.e. one rapid, reflexive response directed at the signal (sign-tracking) and one slower, more flexible response based on expectations about time and place for arrival of the food (goal-tracking). The ecological significance of these two learning systems in cod is discussed.     

Long-term retention of the differential values of Arabic numerals by chimpanzees (<Emphasis Type="Italic">Pan troglodytes</Emphasis>)

As previously reported (Beran and Rumbaugh, 2001), two chimpanzees used a joystick to collect dots, one-at-a-time, on a computer monitor, and then ended a trial when the number of dots collected was equal to the Arabic numeral presented for the trial. Here, the chimpanzees were presented with the task again after an interval of 6 months and then again after an additional interval of 3.25 years. During each interval, the chimpanzees were not presented with the task, and this allowed an assessment of the extent to which both animals retained the values of each Arabic numeral. Despite lower performance at each retention interval compared to the original study, both chimpanzees performed above chance levels in collecting a quantity of dots equal to the target numeral, one chimpanzee for the numerals 1-7, and the second chimpanzee for the numerals 1-6. For the 3.25-year retention, errors were more dispersed around each target numeral than in the original study, but the chimpanzees' performances again appeared to be based on a continuous representation of magnitude rather than a discrete representation of number. These data provide an experimental demonstration of long-term retention of the differential values of Arabic numerals by chimpanzees.     

Quantity-based judgments in the domestic dog (<Emphasis Type="Italic">Canis lupus familiaris</Emphasis>)

We examined the ability of domestic dogs to choose the larger versus smaller quantity of food in two experiments. In experiment 1, we investigated the ability of 29 dogs (results from 18 dogs were used in the data analysis) to discriminate between two quantities of food presented in eight different combinations. Choices were simultaneously presented and visually available at the time of choice. Overall, subjects chose the larger quantity more often than the smaller quantity, but they found numerically close comparisons more difficult. In experiment 2, we tested two dogs from experiment 1 under three conditions. In condition 1, we used similar methods from experiment 1 and tested the dogs multiple times on the eight combinations from experiment 1 plus one additional combination. In conditions 2 and 3, the food was visually unavailable to the subjects at the time of choice, but in condition 2, food choices were viewed simultaneously before being made visually unavailable, and in condition 3, they were viewed successively. In these last two conditions, and especially in condition 3, the dogs had to keep track of quantities mentally in order to choose optimally. Subjects still chose the larger quantity more often than the smaller quantity when the food was not simultaneously visible at the time of choice. Olfactory cues and inadvertent cuing by the experimenter were excluded as mechanisms for choosing larger quantities. The results suggest that, like apes tested on similar tasks, some dogs can form internal representations and make mental comparisons of quantity.     

<Emphasis Type="Italic">Ceteris</Emphasis>-<Emphasis Type="Italic">Paribus</Emphasis> Qualifiers

Antecedent-strengthening, a trivially valid inference of classical logic of the form: P → Q ? (P & R) → Q, has a counterpart in everyday reasoning that often fails. A plausible solution to the problem involves assuming an implicit ceteris paribus (CP) qualifier that can be explicated as an additional conjunct in the antecedent of the premise. The qualifier can be explicated as ‘everything else relevant remains unchanged’ or alternatively as ‘nothing interferes’. The qualifier appears most prominently in the context of the discussion of laws in the sciences, where these laws are often expressed with a CP qualifier. From an analysis of the qualifier’s role in the problem of antecedent-strengthening, we can learn more about CP qualifiers in general and in their application to the laws used in the sciences.