This project will test experimentally a set of hypotheses about monkeys' social knowledge and decisionmaking criteria. One set of experiments will focus on the issue of tactical deception-a phenomenon that has been well documented among apes and some Old World monkeys but virtually never reported in New World primates. Specifically, white-faced capuchins, a New World primate species, will be tested to see whether they find alarm calls less credible when they follow a simulated social situation in which the alarm caller would have a motive to deceive-specifically, a motive to distract the attention of higher-ranking monkeys engaged in an aggressive coalition against him or her. The other set of experiments will focus on the criteria involved in males' decisions about whether to respond aggressively to vocal threats by extra-group males. The project builds on the knowledge that has been gained in observational studies by using playbacks of vocalizations. The investigator will spend several months in Costa Rica conducting observations and collecting the recordings needed for conducting playback experiments. The social relationships and social cognition of capuchin monkeys are an interesting domain of inquiry because of current interest in the evolution of primate intelligence. Capuchins have the largest brains, relative to their bodies, of any nonhuman primates and therefore represent a key data point in the debate about whether the principal driving force behind primate brain expansion was selective pressure for spatial memory and extractive foraging dexterity or for the ability to solve complex social problems. This project will contribute valuable data on social cognition and social relationships in New World primate species that can be compared to the already extensive array of data on such issues in Old World primates. This award will enable the investigator to learn new technical skills, specifically bioacoustic analysis and playback experiment protocols. It will also provide funds for the investigator to conduct experiments to test the feasibility of her approach to the study of the evolution of intelligence.
