The effects of view in depth on the identification of line drawings and silhouettes of familiar objects: Normality and pathology

Three experiments are reported into the effects of viewpoint in depth, and of stimulus type (line drawings vs silhouettes) on picture identification. Clear effects of both factors were observed. Strongly foreshortened views were harder to identify than more canonical views, and silhouettes were harder to identify than line drawings. Furthermore, there was a strong interaction. The foreshortening disadvantage was greatly increased if silhouettes rather than line drawings were presented. Our results suggest that the internal information available in line drawings (but not silhouettes) is critical for identifying foreshortened views of objects. Additional results from an agnosic patient, HJA, suggest that certain forms of brain damage can disrupt the use of internal information for identification, reducing differences between performance with line drawings and silhouettes.