In moral disengagement theory, people can become unethical if they don't see bad sequences of their actions. Therefore, we tent to not tell the truth through email compared to pen and paper.
In many levels, people lie the most via phone and least via email. Face-to-face and instant messages are equal in the middle of other interaction media.
Moral Disengagement Theory
Slide 2
People tend to be more negative toward others via email than with paper and pen.
You can get more honest answers from people if you give them a survey by paper and pen.
People won't give you accurate feedback if you ask them through the telephone. It's better to use pen and paper, or email surveys.
The most efficient and accurate way to get feedback is through the face-to-face method.