Imagine that you were given a strange job where you rode along with the sensory experiences of a mute person, writing their dialog for them. They can hear the dialog you give, including inaudible asides left only for them. You saw and felt all that they see and feel but you can't control their behavior. The job requires you to never admit the situation to anyone, you have to always pretend to be the person under penalty of death, even when talking to them. They're 20 years old now and you've been doing this job your entire life.

How could someone distinguish this setup from how we normally perceive our minds as working?