That’s going to be a hard one to provide definitive answers on. Anecdotally though I saw it with my younger brothers, I saw it with my kids, I have seen it with my friends kids. I am convinced enough, but I will be swayed if someone with the right research and peer reviewed science can make a compelling case. If I had all that I would be presenting my thesis as a best selling book on behavioural psychology, finding a university that would offer me tenure and relaxing into a cushy life of academic celebrity, not posting on Lemmy.