system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do twins often time have different personalities— even if they share the same chromosomes and live in the same environment?
gpt
They don't live in the same environment. They live with each other. While they share the same genetics, they are not treated the same much like any other set of siblings. So each sibling's environment is altered by the other. So whether it's a subconscious need to separate themselves, Experiential vs vicarious learning, etc, they don't lead the same life and are therefore different. 

For example: Twin A gets in trouble for touching a power cord while Twin B watches. Twin A is learning from direct experience and the emotional aspects of discipline, while Twin B is learning vicariously and not the emotional aspect as they aren't in trouble. When we say product of environment, the environment is the interactions you have with it.