The experimenter meets with serious difficulties when he tries to work with complex objects like pictures. The essential nature of experiment is that we should vary the conditions and trace the varying consequences to those varying conditions. Now it is comparatively easy to do this in the case of simple colours and figures. But to change one picture for another may be to introduce a host of differences; and also the effect of a picture on a subject may be so complex that he himself may be misled in saying what elements in the picture appeal to him most. It is therefore not surprising that much still remains to be done in the way of experiments with pictures. Nevertheless many aspects have already been investigated.
It may be well to begin with experiments among children. We shall see that some of the points characteristic of the child's attitude towards pictures remain true even for some adults, especially for those of little general culture and education.
Obviously the first obstacle, in experimenting upon children with pictures, is the difficulty they find in explaining why they like or dislike a picture. It is certainly not fair to assume that they have not marked likings or dislikings for pictures merely because they are unable to give reasons for them. This is often true of adults even when a picture has a very decided attraction for them, or when it repels them, though in the latter case it is usually not so difficult to give a reason.
For these reasons it is much better with young children to take them individually. The tone in which a remark is made may indicate more than the words spoken. This is what I did in my own earliest