The Evolution of Our Preferences: Evidence from Capuchin-Monkey Trading Behavior

Behavioral economics has demonstrated systematic decision-making biases in both lab and field data. But are these biases learned or innate? We investigate this question using experiments on a novel set of subjects — capuchin monkeys. By introducing a fiat currency and trade to a capuchin colony, we are able to recover their preferences over a wide range of goods and risky choices. We show that standard price theory does a remarkably good job of describing capuchin purchasing behavior; capuchin monkeys react rationally to both price and wealth shocks. However, when capuchins are faced with more complex choices including risky gambles, they display many of the hallmark biases of human behavior, including reference-dependent choices and loss-aversion. Given that capuchins demonstrate little to no social learning and lack experience with abstract gambles, these results suggest that certain biases such as loss-aversion are an innate function of how our brains code experiences, rather than learned behavior or the result of misapplied heuristics.Prospect theory, Loss aversion, Reference dependence, Evolution, Neuroeconomics, Capuchin monkeys, Monkey business

Capuchin Brothers vocation brochure

Brochure created to promote vocations for Brothers in the Capuchin order (Capuchin Franciscan Order).https://ecommons.udayton.edu/imri_stokes_vocation/1008/thumbnail.jp

Capuchin vocation brochure

Brochure created to promote vocations for Capuchin order (Capuchin Franciscan Order). It features a personal essay by Brother Martin Pable, O.F.M. Cap., on discerning a call to religious life. More of Brother Martin’s story appears in his book A Call for Me? A New Look at Vocations (Our Sunday Visitor, 1980).https://ecommons.udayton.edu/imri_stokes_vocation/1007/thumbnail.jp

Selfish or altruistic? An analysis of alarm call function in wild capuchin monkeys, Cebus apella nigritus

Alarm calls facilitate some antipredatory benefits of group living but may endanger the caller by attracting the predator's attention. A number of hypotheses invoking kin selection and individual selection have been proposed to explain how such behaviour could evolve. This study tests eight hypotheses for alarm call evolution by examining the responses of tufted capuchin monkeys to models of felids, perched raptors and vipers. Specifically, this study examines: (1) differences between individuals in their propensity to call in response to different threat types, (2) whether there is an audience effect for alarm calling and (3) the response of conspecifics to alarms. Results indicate that the benefits likely to be afforded to the caller vary with stimulus type. Alarm calling in response to felids is most likely selfish, with calls apparently directed towards both the predator and potential conspecific mobbers. Alarm calling in response to vipers attracts additional mobbers as well, but also appears to be driven by kin selection in the case of males and parental care benefits in the case of females. Alarm responses to perched raptors are rare, but seem to be selfish, with callers benefiting by recruiting additional mobbers

Object grasping and manipulation in capuchin monkeys (genera Cebus and Sapajus)

The abilities to perform skilled hand movements and to manipulate objects dexterously are landmarks in the evolution of primates. The study of how primates use their hands to grasp and manipulate objects in accordance with their needs sheds light on how these species are physically and mentally equipped to deal with the problems they encounter in their daily life. We report data on capuchin monkeys, highly manipulative platyrrhine species that usually spend a great deal of time in active manipulation to search for food and to prepare it for ingestion. Our aim is to provide an overview of current knowledge on the ability of capuchins to grasp and manipulate objects, with a special focus on how these species express their cognitive potential through manual behaviour. Data on the ability of capuchins to move their hands and on the neural correlates sustaining their actions are reported, as are findings on the manipulative ability of capuchins to anticipate future actions and to relate objects to other objects and substrates. The manual behaviour of capuchins is considered in different domains, such as motor planning, extractive foraging and tool use, in both captive and natural settings. Anatomofunctional and behavioural similarities to and differences from other haplorrhine species regarding manual dexterity are also discussed

Comparing the cost-effectiveness of methods for estimating population density for primates in the Amazon rainforest Peru

With increasingly extreme fluctuations in flood levels in the Amazon basin (Malhi et al. 2008, Marengo et al. 2012, Bodmer et al. 2014) the future of its' fauna is becoming more uncertain. It is essential therefore that effective monitoring is in place in order to detect drops in population before irreversible damage is done. In developing countries such as the ones situated in the Amazon basin funding for conservation is very limited (Danielsen et al. 2003), it is therefore vital that cost effective methods of monitoring the wildlife of the Amazon are found. Three surveying techniques for monitoring primates are compared in this thesis to find the most cost effective method of estimating population densities of primate species local to the Amazon basin; these are terrestrial transects, aquatic transects and audio-playback point counts. Data was collected in the Pacaya-Samiria National Reserve using these methods over a period of four months, from January to May 2014. For both terrestrial and aquatic transects, transect lines were traversed and data was recorded every time an individual or group of the 7 primates species were spotted. Audio-playback point counts were used to record data for red howler monkeys (Alouatta seniculus)and brown capuchin monkeys (Cebus apella). This was done by mimicking primate vocalisations at a point and recording any resultant responses or sightings of the species under observation. Each survey technique was compared with regards to three qualities; precision, ability to react to change and cost. On average over all 7 species of primate aquatic transects produced the most precise estimations of population density with a mean estimation CV% (percentage coefficient of variance) of 36.35% in comparison the 47.3% averaged by terrestrial transects. Both methods failed to produce precise results for the two rarest species present, the monk saki monkey (Pithecia monachus) and the white fronted capuchin monkey (Cebus albifrons). Aquatic transects were also shown to react to sudden change in population levels. For the two species Alouatta seniculus and Cebus apella aquatic transects once again on average gained the most precise results with a mean estimation CV% value of 20.05% in comparison to the 31.08% of terrestrial transects and 36.35% for audio-playback point counts. The estimates created using audio-playback point counts used considerably less time and resources than the other two methods for single species and was also shown to be the quickest to react to immediate changes in population densities. Thus it was concluded that audio-playback point counts can produce relatively precise estimates that react to population changes at low cost. However only one species can be observed at a time using audio-playback point counts; when observing multiple species at one time it was concluded that aquatic transects are by far the cheapest survey technique and the method that produces precise estimates more consistently. I would therefore recommend for a monitoring effort of several primate species at one given time in the Amazon basin, that aquatic transects be used as it is the most cost-effective overall. However if a single species is a monitoring target, perhaps to be used as an indicator species or because the primate is of most concern, then audio-playback point counts be used as it is possible to gain relatively precise results at a minimal cost. I would also like to suggest that the use of audio-playback point counts be tested on rarer primate species in future as neither terrestrial transects nor aquatic transects could produce a useful estimate in a combined effort of 104 half days. If audio-playback point counts could be used to get good estimates for rare primate species then monitoring strategies could be developed combining the use of audio- playback point counts and aquatic transects to gain precise density estimates for all primate species in an area whilst keeping costs low. A generic decision tree is presented at the end of this thesis as a guideline to cost-effective primate monitoring for any seasonally flooding rainforest study site

Visible spatial contiguity of social information and reward affects social learning in brown capuchins (<i>Sapajus apella</i>) and children (<i>Homo sapiens</i>)

Animal social learning is typically studied experimentally by the presentation of artificial foraging tasks. Although productive, results are often variable even for the same species. We present and test the hypothesis that one cause of variation is that spatial distance between rewards and the means of reward release causes conflicts for participants’ attentional focus. We investigated whether spatial contiguity between a visible reward and the means of release would affect behavioral responses that evidence social learning, testing 21 brown capuchins (Sapajus apella), a much studied species with variant evidence for social learning, and 180 two- to four-year old human children (Homo sapiens), a benchmark species known for a strong social learning disposition. Participants were presented with a novel transparent apparatus where a reward was either proximal or distal to a demonstrated means of releasing it. A distal reward location decreased attention towards the location of the demonstration and impaired subsequent success in gaining rewards. Generally, the capuchins produced the alternative method to that demonstrated whereas children copied the method demonstrated, although a distal reward location reduced copying in younger children. We conclude that some design features in common social learning tasks may significantly degrade the evidence for social learning. We have demonstrated this for two different primates but suggest that it is a significant factor to control for in social learning research across all taxa

Face processing limitation to own species in primates: a comparative study in brown capuchins, Tonkean macaques and humans

Most primates live in social groups which survival and stability depend on individuals' abilities to create strong social relationships with other group members. The existence of those groups requires to identify individuals and to assign to each of them a social status. Individual recognition can be achieved through vocalizations but also through faces. In humans, an efficient system for the processing of own species faces exists. This specialization is achieved through experience with faces of conspecifics during development and leads to the loss of ability to process faces from other primate species. We hypothesize that a similar mechanism exists in social primates. We investigated face processing in one Old World species (genus Macaca) and in one New World species (genus Cebus). Our results show the same advantage for own species face recognition for all tested subjects. This work suggests in all species tested the existence of a common trait inherited from the primate ancestor: an efficient system to identify individual faces of own species only

Tactile information improves visual object discrimination in kea, Nestor notabilis, and capuchin monkeys, Sapajus spp.

In comparative visual cognition research, the influence of information acquired by nonvisual senses has received little attention. Systematic studies focusing on how the integration of information from sight and touch can affect animal perception are sparse. Here, we investigated whether tactile input improves visual discrimination ability of a bird, the kea, and capuchin monkeys, two species with acute vision, and known for their tendency to handle objects. To this end, we assessed whether, at the attainment of a criterion, accuracy and/or learning speed in the visual modality were enhanced by haptic (i.e. active tactile) exploration of an object. Subjects were trained to select the positive stimulus between two cylinders of the same shape and size, but with different surface structures. In the Sight condition, one pair of cylinders was inserted into transparent Plexiglas tubes. This prevented animals from haptically perceiving the objects' surfaces. In the Sight and Touch condition, one pair of cylinders was not inserted into transparent Plexiglas tubes. This allowed the subjects to perceive the objects' surfaces both visually and haptically. We found that both kea and capuchins (1) showed comparable levels of accuracy at the attainment of the learning criterion in both conditions, but (2) required fewer trials to achieve the criterion in the Sight and Touch condition. Moreover, this study showed that both kea and capuchins can integrate information acquired by the visual and tactile modalities. To our knowledge, this represents the first evidence of visuotactile integration in a bird species. Overall, our findings demonstrate that the acquisition of tactile information while manipulating objects facilitates visual discrimination of objects in two phylogenetically distant species