Upper left panel: Mean (± SEM) numbers of cocaine infusions obtained by pressing the cocaine work lever in the Closed (black bars), OpenCoc (white bars), and OpenSac (gray bars) groups across the range of FRs tested. Data are averaged over the three sessions at each FR. Upper right panel: Mean (± SEM) numbers of saccharin infusions obtained by pressing the saccharin work lever in the three groups. Lower left panel: Mean (± SEM) numbers of additional cocaine infusions or saccharin reinforcers obtained by the OpenCoc and OpenSac groups, respectively, by pressing the middle lever. Lower right panel: Mean (± SEM) numbers of total (work lever plus middle lever) cocaine infusions or saccharin reinforcers per session obtained by the OpenCoc and OpenSac groups, respectively.