The broad objective of this proposal is to test in a nonhuman primate model two aspects of cognition considered a trademark of human-unique thinking: sensitivity to phoneme sequences for parsing language, and judgments of intentionality from actions. Tamarins are selected as the species of choice due to their unique reliance on cooperative breeding, their demonstrated social tolerance, their sensitivities to communicative sounds and music, and their spontaneous use of social abilities. Recent scrutiny generated by a retracted publication and a Harvard investigation judgment of research misconduct specifically related to published studies of tamarins in these areas by Marc Hauser's lab makes it imperative to retest such abilities in an independent lab. This research determines whether a species of a New World monkey, one which split from a common evolutionary lineage with humans 40 million years ago, can discriminate sequence changes used in human language parsing and can think about the intentions and goals of others based on their actions and on inferring what they "know." Research using monkeys as a model to test human-like cognition reveals the brain processes necessary to generate abstract thinking, both in language learning and social awareness. The tests of phoneme sequence discrimination are accomplished by a habituation procedure using 3-phoneme sequences that fit an AAB pattern or an ABB pattern. Violations of the pattern and introduction of novel phonemes in previously habituated sequences are test items and dishabituation is measured through look rates toward the sound and through inhibited eating due to increased attention. These tests are also extended to music and to monkey calls to examine generalization of the sequence sensitivity. Intentionality is tested in two experiments, one involving a choice response following an experimenter's pointing gesture and one involving copying the response of a model in order to get rewards. The first experiment manipulates the knowledge base of the experimenter to test whether tamarins consider whether the person pointing actually knows the location of the hidden food or should not know. The second experiment uses a variety of models, including tamarins, humans, and ghosts (or responses made by invisible wires) in order to test whether tamarins copy more accurately with a live agent when its intentions can be inferred.
The relevance of this project to public health is that it examines two trademark human cognitive abilities, abstract language sensitivities and inference of intention and goal, in a simpler animal model. If one can determine definitively these types of human-like thinking in a primate remotely related to humans, having branched off of common evolutionary lineage 40 million years ago, the brain structures and thinking processes needed to support language and inferential thought in a social context are revealed. The project also completes the scientific process by re-examining important questions related to primate cognition and the evolution of the human mind that have fallen under scrutiny.