Instrumental responding under a progressive schedule or a risk of punishment risk.

<p>(<b>A, B</b>) Instrumental responding under a progressive ratio (PR3) schedule was elicited as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0096787#s2" target="_blank">Methods</a>. The graphs show the breakpoints reached by each individual animal. The horizontal bars indicate the group mean and SEM. Panel A shows the results for a group of 10 male mice that was sequentially tested under PR3 schedules of access to saccharin and ethanol. Panel B represents 3 separate groups of 10 females each that were tested under PR3 schedules of access to saccharin, alcohol or water. (<b>C, D</b>) Instrumental responding with the risk of punishment. The mice were provided with FR3 instrumental access to alcohol, saccharin or water. Panel C shows the numbers of bottle licks performed by individual male mice (the same cohort shown in A) that were tested in separate intervals of access to saccharin or alcohol. During the first session, there was a 100% risk of punishment immediately after the FR3 was completed. During the second and third sessions, the punishment risk was 25%, and punishments were delivered 2 seconds after completing the FR3. Panel D shows the numbers of bottle licks performed by the individual mice of three cohorts that were separately tested with a 25% risk of punishment delivered 2 seconds after the FR3 was completed; these are the same cohorts of mice shown in panel B. The horizontal bars indicate the group means and SEMs. The statistical analysis of the group means in Panel D was performed via one-way ANOVA (F_2,29 = 8.188 P<0.01, Tukey's HSD <i>post hoc</i> P<0.05 * saccharin vs. water).