Ricky Parsons (2000) was interested in exploring how tamarins might form categories for different groupings of animals, and we worked together to develop a project for his senior thesis, with the help of other students working with the monkeys. Tamarins living in our lab had not seen the outside world much and had not run into other species of primates or other mammals (other than humans), or reptiles. Moreover, we decided to use a category of animal that no longer exists, dinosaurs, since they possess features that very broadly overlap with birds, reptiles, and mammals. Neiworth hypothesized that the broadness of this category would be based on what the subjects, our monkeys, were familiar with seeing (and this explains expert categorization by people trained to note differences within dog species, or cars, or birds). We started by exposing the tamarins to pictures of only one species of monkey other than their own (either golden lion tamarins or pygmy marmosets). Then, we used dishabituation techniques to see if they would prefer to look at novel pictures of a new species rather than novel pictures of the same species they had seen before. We then broadened the primate category that they experienced to 4 species of monkeys, and tested them with additional novel pictures. We broadened the category even further to include apes, and tested the tamarins with novel pictures of species in those categories as compared to non-primate mammals. Read the article below to get a real sense of what we found! It’s fascinating!