It's reliable across different populations and has been demonstrated in monkeys (non-apes), for which the existence of culture may be more more doubtful. It's

It's reliable across different populations and has been demonstrated in monkeys (non-apes), for which the existence of culture may be more more doubtful. It's pretty easy to replicate, here's an example: https://www.youtube.com/watch?v=Bm9xXyw2f7g https://www.youtube.com/watch?v=Bm9xXyw2f7g