I wonder if you could predict if someone prefers to enter numbers using the top row of the keyboard vs the numeric pad by asking them to create a long random number.
Obviously, people will have a tendency to not reuse the same finger twice in a row, and also not use a key adjacent to the previous key.
The question is… what’s the shortest number you can ask someone to generate and get a good idea of which input method was used, and what’s the shortest number to determine if it was a truly random number or a human generated random number.