Fig 1. Overall observing rates (top three panels) separated by multiple schedule component (middle three panels), and food-key response rates (bottom three panels) during each of the final six sessions of each condition of Experiment 1.

The condition headings refer to the schedule of conditioned reinforcement in effect. The filled circles denote response rates during the VI component of the multiple VI Ext schedule, and empty circles denote response rates during the Ext component. Dissociated rates of observing (middle) and food key (bottom) responding were lost for the sixth session in the third condition and the fifth session of the third condition for Pigeons 200 and 166, respectively.