Picture perception in birds: Perspective from primatologists

In their target article, Weisman and Spetch (2010) question the validity of pictures to present real things to birds, mostly because pictures are primarily made for the human eye, and not for the eye of birds with different functional properties. Here, we argue that this issue of picture validity is similarly critical for primatologists, even when they study the "higher" nonhuman primates with a more similar visual system, and emphasize cognitive limitations in referential abilities that may be an important source of differences in picture processing modes between human and animals. In their target paper, Weisman and Spetch (2010) review the literature on picture perception in birds and adequately question the validity of pictorial stimuli (photographs, digitized pictures, and movies) to present real objects or scenes to these animals. In their review, they raise the important issue that with the current technology, pictures are primarily designed to be perceived by human eyes and might therefore, not be well adapted to birds possessing a different visual system. They document the risk for anthropocentric errors in experimental research using pictures with birds, and call for new empirical evidence showing a correspondence between the perception of pictures and the perception of objects in birds. Despite the widespread use of pictures in animal psychology, investigators have rarely questioned the realistic nature of pictures and their ecological validity. In that respect, Weisman and Spetch's paper (2010) is among the very few to explicitly do so (see also Cabe, 1976, Fagot 2000). They must be applauded for bringing back this important issue to the attention of the field. In general, we are supportive of their position that a greater care must be given to the use of pictures in experimental animal research. However, consideration of the primate literature suggests that