When was the first time you felt invisible? When was the last time you looked right through someone, as if he wasn’t there? Director Christopher McElroen posed those questions to his cast when he began rehearsing the stage adaptation of “Invisible Man.” He asked the actors to fill out a form with 25 questions, probing their personal experiences about loss of identity.

“We’ve all felt invisible at one time or another,’’ McElroen says. For instance: He recalls moving from California to New York when he was a small boy. He skipped the second grade and went directly to third grade, but he was required to go to the second-grade class for reading. He felt as if the teacher and the students in reading class didn’t even see him, so for two weeks, he hid in the all-purpose room and daydreamed. “I chose invisibility for myself, but my teachers eventually found out. Needless to say, I wasn’t invisible anymore.”