Cropper, F. A. (1935). An experimental evaluation of the ability of children to interpret pictures used in elementary textbooks in geography. The Journal of Geography, 34(3), 89-101.

(The problem.) The primary aim of this investigation was to determine the influence of instruction on the ability of elementary grade children to interpret geographic textbook pictures. Textbook illustrations were used rather than stereopticon views or moving pictures because the visual instruction in most schools is still limited to the class room textbook. It was not our purpose to advance any particular method by which picture study may be made or to defend the type of pictures used in certain textbooks. The problem concerned itself with what instruction has to do with enabling the child to interpret geographic pictures and not how he is to secure the specific training.