I've encountered another type of "blind drawing" in many art classes. The exercise is to spend five or ten minutes looking at a subject, then turn away from the subject and draw what you remember. After you've finished the drawing, turn around again and compare the subject to the image you retained. The differences are usually very dramatic. It's a helpful technique to train the artist's eye to remember more than the average viewer's eye, and to discover what you consider to be important in the subject.