Yeah, it's fairly well known and researched. Here's a randomly selected study from Harvard: https://henrich.fas.harvard.edu/publications/cultural-variations-childrens-mirror-self-recognition > The first experiment shows that only 2 out of 82 [2.4%] 18- to 72-month-old Kenyan children manifested self-oriented behaviors toward the mark, most of them freezing while staring at their specular image. This result is in sharp contrast with the multiple studies reporting that by 20 months of age, 60% to 85% of Western middle-class children pass the mark test