Im surprised to hear that. I went to Caltech for my postgrad and never collaborated on an test, and it would have never ocurre me to do so (and no, the professor didn’t have to explicitly say they collaboration was not allowed. It was just the standard honor code).
We all suspected of people that didn’t adhere to the honor code and it was frowned upon, and they could have faced repercussions if anyone had reported them.
We all suspected of people that didn’t adhere to the honor code and it was frowned upon, and they could have faced repercussions if anyone had reported them.