A number of students were interested in studies of feature detection in people and tamarins, and the tamarin work had led us to focusing on perceptual uniqueness shown by people with autism that seemed similar to trends shown by the tamarins. Specifically, tamarins did not automatically prefer to judge objects by global shape, rather they seemed to process local detail and global shape equivalently. We thought perhaps they looked at faces differently than humans as well, and at the time, many labs were presenting inverted faces to people and different species of monkeys to see if primates processed faces more wholistically, as did humans. Specifically, humans do not readily and quickly identify the identity of inverted or upside-down presentations of human faces, chiefly because the presentation scrambles the relative location of eyes, nose, and mouth and we rely on the placement of these components relative to each other to identify a face.
To this end, Janice Hassett and Cara Sylvester (2003) worked together to test tamarin monkeys on differently oriented human faces, tamarin faces, chimpanzee faces, and a variety of common lab objects. Below is an example of the stimuli we used in a look rate study.
Examples of human faces (the construction workers who worked that summer) and tamarin faces, our friends in the lab.
We found that college students would quickly notice new human faces compared to ones they had just seen. When all the human faces were inverted, the students did not show the same reaction because they could not notice which of the 2 faces was new. Additionally, college students did not notice new chimpanzee or tamarin faces, even when they were presented upright and in an orientation that could be processed holistically.
In contrast, tamarins noticed new human faces and new tamarin faces compared to ones they had just seen, but not new chimpanzee faces. Even more interesting, tamarins failed to show this quick attentional ability when human and tamarin faces were inverted.
Read the published article on face processing (2006).
CITATION: Neiworth, J. J., Hassett, J. M., & Sylvester, C. J. (2007). Face processing in humans and new world monkeys: the influence of experiential and ecological factors. Animal cognition, 10(2), 125–134. https://doi.org/10.1007/s10071-006-0045-4
View the poster on face processing presented at the Annual Meeting of the Midwestern Psychological Association (2003).