I understand the task of a 2AFC test is to select one of the two stimuli presented (e.g. the stronger one), whereas in Yes-No test there is only one stimulus presented. But is it ok to ask a Yes-No question (e.g. was there a difference between A and B?) in a test with 2 stimuli? and can it still be called a 2AFC test? (Or is it valid to do Yes-No test with two stimuli?)
I am asking this with regard to a threshold test using a 2AFC transformed staircase (2 down 1 up procedure). It'd be a lot easier for subject to respond whether there was a perceivable difference between two stimuli rather than having to choose the stronger one. As my main interest is to see just noticeable difference, which is stronger is not of a concern. However, I guess there must be a specific reason why one stimulus has to be chosen over the other in a 2AFC test (re bias and sensitivity?). And I wonder what would be the implication of using a Yes-No question instead.
Many thanks in advance for your answers.