The perceptual bases of visual literacy are explored, drawing on research into the interpretation of pictures by viewers not familiar with pictorial representation. Research has indicated that inexperienced viewers do not find it difficult to recognize pictures that may be discrepant in color or shape from a familiar object, but may be troubled by the perception of depth in pictures. Reasons why this phenomenon should be so are explored; and it is suggested that the puzzlement of inexperienced viewers may be due to unfamiliarity with the pictorial media, rather than a response to the content of the pictures. It is precisely because of their accessibility to the untutored viewer that images as a mode of communication may be unmatched in their capacity for manipulation and misinformation. The need for visual literacy in its broadest sense--i.e., as reflective, critical awareness of visual conventions and their uses--should be correspondingly acute. (Contains 25 references.) (SLD)