When you have a body and a brain based on the exact same DNA as someone else, things tend to work the same way.
Our brains tend to make the same connections between things, reach similar conclusions, and get confused on the same topics. This is why we know sit far apart when taking an exam in the same room as each other. Because getting the same wrong answer to the same question tends to puzzle the teacher.
Our seventh grade science teacher assigned seating, and I was way up front to the right, and Baby A was in the last desk in the back on the left. No one got up during the test. We both missed one question, the same one, and marked the same wrong answer. Clearly we didn't cheat, and the teacher briefly mused on the unlikelihood of telepathy.
We sat kind of close to each other in a midterm last quarter, and got the same wrong answer to a question. (We each missed more than one for sure). Same wrong answers trigger more suspicion than same right answers (because it's right for a reason, of course). We didn't cheat, it would have been obvious to the teaching assistants and professor if I positioned myself in a way to see Baby A's test or vice versa. But since then, we have been careful to get to exams early to pick seats far away from each other, so there is no possibility of that ever being accused of happening.
I guess I haven't recovered from being accused by our second grade teacher of cheating. We sat at the same group of desks, so OBVIOUSLY those DEVIOUS, TRICKY IDENTICAL TWINS used their external hard drives (each other's brains) for help. Actually, we didn't, and I'm pretty sure I cried when the teacher said we did. Because I was that much of a sensitive two shoes. It was pretty clear to everyone else that those gosh darn goody goodies wouldn't cheat. Our classmates also totally thought the teacher was on crack. Or however a second grader would say that.