Our lab has tried to test whether tamarins can show awareness of others in order to work together to solve a problem. In the first instance, we tried in 2009, Julia Greenberg’s senior thesis focused on whether tamarins could learn that pulling a string would pull toward them a reward box to obtain treats, and then could use this information when the string ends were set very far apart such that 2 tamarins who are cage mates would have to pull at each end simultaneously in order to move the reward box. We found that about 30% of the tamarins who understood the task when operating it alone could work with other tamarins to operate it cooperatively. We presented this work in 2009, and Julia Greenberg went on to Max Planck Institute to investigate similar questions in chimpanzees. She has since obtained a PhD in zoology/animal behavior from Michigan State University.
The second study was done in 2018-2019 by Chris Leppink-Shands for his senior thesis project. Chris used a button box and tamarins first learned to push a button to obtain a cheerio. Then if they pushed their button when Chris pushed his, they could obtain 2 cheerios. Two monkeys tested in this way switched to pushing their button along with Chris to increase rewards.