I remember reading about a study [1] that showed that humans recognize faces based on how similar they are to the faces of their parents. It's well known that humans are more easily able to differentiate faces within our own races. But what the study did was look at people who were adopted by parents of a different race. Those people were more easily able to differentiate faces of people of the same race as their adopted parents and had difficulty differentiating faces of people of their own race. The inference is that we actually store/recognize facial deltas, not full facial images.

I'm curious how this study would explain or contradict the results of that study. Also, were the monkeys raised by monkey parents or human scientists? Monkeys that were allowed to imprint on humans might be more similar to humans and, yet, unrepresentative of monkeys.

[1] I think it was https://www.ncbi.nlm.nih.gov/pubmed/15943669