The International Research Fellowship Program enables U.S. scientists and engineers to conduct nine to twenty-four months of research abroad. The program's awards provide opportunities for joint research, and the use of unique or complementary facilities, expertise and experimental conditions abroad.
This award will support a twenty-four-month research fellowship by Dr. Brandon C. Wheeler to work with Dr. Julia Fischer at the German Primate Center in Gottingen, Germany with field work done at Iguazu National Park in Argentina.
The cognitive abilities of primates are argued to have evolved so that individuals can outwit group-mates in competitive interactions by using, among other tactics, deceptive and counterdeceptive behaviors. However, because such behaviors are rare, the proximate mechanisms underlying these behaviors have not been examined in wild primates and it is thus unknown if they are indeed driven by cognitive mechanisms. Recent work by the PI with wild tufted capuchin monkeys in northeastern Argentina has shown that these primates use alarm calls (i.e., vocalizations normally given in response to predators) during feeding but when no predators are present. The calls often cause dominant individuals to run out of the food patch and allow the more subordinate caller to gain access to the food. However, listeners reduce the success of these deceptive alarms by ignoring them more often than they do honest alarms. As the first systematic evidence of deception and associated counter-deception in wild primates, this presents an ideal study system to examine if cognitive abilities are necessary to explain the observed behaviors.
In the current study, the PI is investigating the mechanisms underpinning the observed deceptive and counter-deceptive behaviors in the same population of Argentine capuchin monkeys. Specifically, this study addresses two questions. First, because previous studies have indicated that alarm calling behaviors may be controlled by the production of cortisol, a hormone associated with stress, is it possible that deceptive alarms are driven proximately not by cognitive mechanisms, but by hormonal reactions to competition-induced stress? Second, is counterdeception better explained as a recognition of subtle acoustic differences between honest and deceptive alarm calls, or as skepticism of calls given in competitive contexts? The first question is addressed by experimentally manipulating food distribution and measuring the levels of cortisol excreted in the feces of dominant and subordinate individuals. The second question is addressed by analyzing audio recordings of honest and deceptive alarm calls to determine if they differ acoustically, and by playing audio recordings of deceptive alarm calls to the subjects in noncompetitive contexts to determine if they respond with antipredator reactions more often in the latter context than they do during competitive feeding contexts. Hormonal and bioacoustic analyses are being conducted at the German Primate Center in Göttingen, Germany. The results will elucidate the degree to which cognition underlies the deceptive and counterdeceptive behaviors observed in this species and may provide insight into the evolutionary origins these behaviors in humans.
Beyond the project's intellectual merit, this grant funds training for a young US researcher in laboratory analyses which are increasingly being used to understand the evolution of behavior in primates and other animals. Such knowledge will prove critical as the PI moves forward in his teaching and research career, as will the collaborative relationships developed between the PI and international research institutions during the funding period.
Like many species of primates and birds, tufted capuchin monkeys warn group members of the presence of predators by giving alarm vocalizations when they spot cats or snakes. In addition to these "honest" alarm calls, wild tufted capuchins in Iguazú National Park, Argentina have been shown to use alarm calls deceptively to distract group-mates during feeding in order to increase access to contested food resources. However, listeners do not always fall for the trick - they seem skeptical of alarm calls given during feeding, possibly because they are skeptical of such calls, having learned that they are less likely to be an honest indicator of the presence of a predator. While such behaviors bear a strong resemblance to human behaviors that we would consider deceptive or counter-deceptive (that is, those behaviors we use to counteract another individual’s deception), seemingly complex behaviors in animals are often underpinned simpler processes than those that underlie similar behaviors in humans. This NSF funded project aimed to determine the degree to which deception and counter-deception in the tufted capuchin alarm call system is underpinned by cognitive mechanisms, and in doing so has made several unique contributions to the fields of anthropology and psychology. The projected tested whether the behaviors could be explained by relatively simple mechanisms. For example, stress could be a driving factor in the production of false alarms, much in the same way that a person’s stress may be, consciously or unconsciously, manifested in a discontented vocalization. Likewise, slight differences in the way that honest and deceptive alarm calls sound could explain why listeners often ignore deceptive calls. Notably, the results of the project did no lend support to either of these relatively simple mechanisms. The conditions that lead to deceptive alarm calls did not lead to increased stress, and although there are some slight differences in the acoustic structure of honest and deceptive alarms, listeners do not seem to cue in on these differences. While it’s still not clear how much cognition is involved in the production of deceptive alarms, it seems that listeners ignore deceptive alarm calls more than honest ones because they have learned that alarm calls that are given while competing for food are not very reliable indicators of the presence of a predator. Although such behavior has some sort of cognitive basis, additional research will be needed to determine exactly how cognitively taxing it actually is. This study was the first attempt to investigate the mechanisms underlying deception and counter-deception in any wild primate, and provides insight into the degree to which an ability to employ deception and counter-deception may have contributed to the evolution of increased brain size and cognition in primates. More broadly, the project allowed for the formation of ties between US and foreign (German and Argentine) researchers. It also provided hands-on training in field methods for studies of animal behavior for several young biologists (from the US, Argentina, Peru, and Ireland), as well as funds to maintain the biological field station in Iguazú National Park, Argentina. Further, the fieldwork was conducted with assistance of an individual of the local indigenous Guarani population. This has an impact beyond this single individual, as it concretely demonstrates the benefits of the preservation of natural resources for local populations.
