Examples of multi-item displays used in Young & Wasserman (1997), ranging from a same (OD/16S) to different display (16D/0S). The labels represent how many items in the display were different and same. Note. From Figure 5, “Entropy detection by pigeons: Response to mixed visual displays after same-different discrimination training,” by M. E. Young and E. A. Wasserman, 1997, Journal of Experimental Psychology: Animal Behavior Processes, 23, p. 163. Copyright 1997 by the American Psychological Association. Adapted with permission.