Hypoxia training
In the US, hypoxia training is encouraged but is optional. There is a program to provide civil pilots access to Air Force physiological training including an altitude chamber. I did a one day training that included lecture, learning various O2 systems, and experiencing hypoxia at cruise and as a rapid decompression. I still have a worksheet that they had us do at FL290 after removing O2. It has simple math problems and other simple tasks such as signing your name and connecting the dots. It is very instructive to see how your ability even to sign your name deteriorates over a few minutes time. The idea is fir each person to experience their symptoms. Very valuable and while it was part of my college program, it is not required by the FAA.