This is because noise in instructional images is filtered out for students, denying them opportunities to develop their own skills in interpreting what elements are important to attend to. Students who have had experience deciphering information from realistic noisy detail are better able to transfer such skills. Visual literacy research has been helpful in translating psychological principles into techniques for the evaluation and production of visuals. One popular hypothesis on the perception of colour images is that they are rapidly and therefore easily readable. The assumption often is that the inclusion of realistic illustrations and photographs will not hinder, if they do not improve instruction.
Illustrations can confuse as well as illuminate.
Visual literacy posits that different visuals communicate a different degree of reality. Thus, all images are not equally and easily readable. No single instructional image can contain all the attributes necessary for it to be appropriate for all instructional objectives. There are no universally communicable images. Rather, an illustration with certain attributes, shaped by a well-drafted caption, may be ideal for specific applications.