No evidence for feature binding by pigeons in a change detection task

• We used a change detection task to study feature binding in visual short-term memory.
• Unlike people, pigeons showed no evidence of feature binding.
• Follow-up tests disclosed that pigeons relied on the change in display variability.
• A better task to study binding might require attending to changes in individual objects.

We trained pigeons to respond to one key when two consecutive displays were the same as one another (no-change trial) and to respond to another key when the two displays were different from one another (change trial; change detection task). Change-trial displays were distinguished by a change in all three features (color, orientation, and location) of all four items presented in the display. Pigeons learned this change-no change discrimination to high levels of accuracy. In Experiments 1 and 2, we compared replace trials in which one or two features were replaced by novel features to switch trials in which the features were exchanged among the objects. Pigeons reported both replace and switch trials as “no-change” trials. In contrast, adult humans in Experiment 3 reported both types of trials as “change” trials and showed robust evidence for feature binding. In Experiment 4, we manipulated the total number of objects in the display and the number of objects that underwent change. Unlike people, pigeons showed strong control by the number of feature changes in the second display; pigeons’ failure to exhibit feature binding may therefore be attributed to their failure to attend to items in the displays as integral objects.