“Non-shared environment” just means anything that differs between the two kids. This could include their different treatment by the same adults, their different

“Non-shared environment” just means anything that differs between the two kids. This could include their different treatment by the same adults, their different choices of activities, differences in the subconscious mental processes, their different adopted roles inside the family, their different diseases or injuries, their asymmetrical relationship with each-other, etc. It doesn’t have to be outside the home. Twin studies don’t reveal exactly what the causes were of different outcomes. All they can do is statistically split causes into broad classes based on the differences between twins raised together or apart and based on the differences between identical vs. fraternal twins.