It was a test that was used to determine whether an individual can recognize that they are the reflection in the mirror. After some overseas tests began to show a stark difference between white and black children, it was quickly explained as "cultural differences" and shut down. It has rarely used since and if you search it, you won't find anything that talks about race, only "western children" and "[nationality] children". https://journals.sagepub.com/doi/abs/10.1177/0022022110381114 >Western children first show signs of mirror self-recognition (MSR) from 18 to 24 months of age, the benchmark index of emerging self-concept. Such signs include self-oriented behaviors while looking at the mirror to touch or remove a mark surreptitiously placed on the child’s face. The authors attempted to replicate this finding across cultures using a simplified version of the classic “mark test.” >In Experiment 1, **Kenyan children (N = 82, 18 to 72 months old) display a pronounced absence of spontaneous self-oriented behaviors toward the mark**. .