When it comes to useful psychological experiments about Human nature, I think that the Stanford Prison Experiment is a very useful one to understand ourselves and the problems we are going through.
It basically showed that in the “right” conditions any of us could become a “concentration camp guard”, happily enjoying abusing others.
While it is a terrible, revolting discovery and many people tried to deny the results or use all kinds of excuses to discredit it, in fact, we are born with an inherently selfish, individualistic, and exploitative nature that enjoys succeeding at the expense of others.
The most important thing is that until we recognize these “dormant” or carefully, mostly subconsciously masked traits in ourselves, we can never learn how to correct, neutralize them.
This is why we are unable to build sustainable, positive connections, cooperation between us and keep falling back into the same self-serving- self-justifying traps, instincts, which is causing the recurring, vicious historic cycles we go through and the general direction of Human society towards self-destruction.