JOURNAL OF THE EXPERIMENTAL ANALYSIS OF BEHAVIOR PIGEONS' DISCRIMINATION OF PAINTINGS BY MONET AND PICASSO SHIGERU WATANABE, JUNKO SAKAMOTO, AND MASUMI WAKITA KEIO UNIVERSITY Pigeons successfully learned to discriminate color slides of paintings by Monet and Picasso. Following this training, they discriminated novel paintings by Monet and Picasso that had never been presented during the discrimination training. Furthermore, they showed generalization from Monet's to Ce- zanne's and Renoir's paintings or from Picasso's to Braque's and Matisse's paintings. These results suggest that pigeons' behavior can be controlled by complex visual stimuli in ways that suggest categorization. Upside-down images of Monet's paintings disrupted the discrimination, whereas in- verted images of Picasso's did not. This result may indicate that the pigeons' behavior was controlled by objects depicted in impressionists' paintings but was not controlled by objects in cubists' paintings. Key words: stimulus control, concept, pattern discrimination, vision, key peck, pigeon When we see paintings by Picasso and Mo- net, we can with some accuracy recognize which is Picasso's and which is Monet's, even if we have never seen the particular paintings be- fore. There are many possible cues for this discrimination, such as color, style of brushing, favorite subjects, and so on, but no single fea- ture differentiates each artist. It is also clear that we have acquired such visual concepts of paintings of Picasso and Monet by experience. Can pigeons discriminate paintings of one art- ist from those of another artist? If they can, do they also show generalization to paintings of other artists belonging to the same group, such as an impressionist or a cubist? Porter and Neuringer (1984) reported successful learning of musical discrimination of Bach and Stravinsky by pigeons. Can pigeons discrimi- nate visual arts also? Birds have excellent visual ability compa- rable to that of humans, and there have been many experimental studies showing acquisi- tion of visual concepts in birds. Since Herrn- stein and Loveland (1964) successfully trained pigeons to respond to color slides on which a human being appeared and not to respond to those without a human, there have been many studies demonstrating learning to discriminate natural concepts (e.g., Cerella, 1979; Herrn- The authors wish to express their gratitude to R. J. Herrnstein for encouragement and comments on this re- search. This research was supported by Grant-in-Aid for Promotion of Sciences 05206113. Address correspondence and reprint requests to Shigeru Watanabe, Psychology Department, Keio University, Mita 2-15-45, Minato-ku, Tokyo, Japan. stein & de Villiers, 1980; Herrnstein, Love- land, & Cable, 1976; Roberts & Mazmanian, 1988; Watanabe, Yamasita, & Wakita, 1993), artificial concepts (Bhatt, Wasserman, Reyn- olds, & Knauss, 1988; Watanabe, 1991), and symmetry of objects (Delius & Habers, 1978). Most of these natural-concept experiments used a slide projector as the stimulus-presen- tation device, and pigeons showed transfer of discrimination of photographs to real objects and of real objects to photographs (Watanabe, 1993). Representational paintings have fea- tures similar to photographs, but paintings patterned after impressionism are not precise reflections of the real world. They often are considered to be a reflection of the artist's sub- jective world. We can, however, identify "ob- jects" in the paintings by Monet, Renoir, and Cezanne. In other words, we find a relation between these paintings and real objects. How- ever, such a relation is often weak in the paint- ings by Picasso, Matisse, and Braque. Realism is relevant only for a perceiver who can see a painting as a representation of a three-dimen- sional world. If realism makes a difference to a pigeon, we can presume that it can see a painting as a representation of a three-dimen- sional world. EXPERIMENT 1 In this experiment pigeons were trained on a discrimination between photographs or vi- deos of paintings by Monet and those of Pi- casso. The paintings differed in their color, sharpness of contour, and objects. Potential cues for discrimination were examined by as- 165 1995, 639 165-174 NUMBER 2 (MARCH)