Johnstone's teachings Whilst he was running the Writer's Group at the Royal Court, he began to teach that drama occurs from dynamic levels of status. He came to this realisation as a result of reading several books by Desmond Morris. Johnstone was the first theatre professional to introduce the term "status transactions" into modern theatre,[citation needed] believing that a high proportion of drama comes from the multiple and tiny ways that people attempt to get what they want by raising or lowering their social status. His teaching included exercises in which students practiced a low-status role by entering the classroom, and acting as though they were accidentally interrupting a very important meeting. The exercise was then repeated by the student. In Impro: Improvisation and the Theatre, Johnstone reports that the increased shows of deference that students acted out often triggered uproarious laughter in the class. He attributes this to a deep-seated human interest in the acting out and renegotiation of status roles. One of Johnstone's major interests is the use of masks and costumes which represent different emotional states and social roles. He found mask-work to be a powerful learning device. The student's ability to be "in the mask" became so powerful that several fellow instructors reported they were afraid to allow students to use masks in class because some students became overtaken by the mask character. In Impro: Improvisation and the Theatre, he speculates that this effect occurs because masks allow students to let go of their day-to-day identity, especially after the effective exercise of seeing and acting out their new identities before a mirror.