What we did....
Two members of our group (As) were shown a picture in class - no-one else in the group got to see it.
Two members of the group (Bs) discussed what the picture was like with the As then walked down the corridor to tell the Cs what to draw.
Two members of our group (Cs) waited in another classroom - ready to draw a copy of the picture.
After 20 mins, we compared the two pictures to see how successful we were.