Statistics were performed using JMP 7.0.1 (2007, SAS Institute Inc.). Shapiro-Wilk tests were used to establish normality and Levene’s test to establish homogeneity of variance. Non-parametric tests were used primarily because the small sample size (N=8 per strain per condition for conditioned preference experiments) often resulted in non-normality and lack of homogeneity of variance within the data. In addition, we chose to non-parametric tests because they tend to be more conservative than their parametric equivalents. Wilcoxon tests were used to compare performance indices to zero. Kruskal-Wallis tests followed by Students-t, Tukey’s or Dunnet’s post-hoc tests were used to compare the performance indices between groups. For ethanol hyperactivity assays, repeated measures ANOVA was used to compare activity between groups. Significance was marked at p<0.05. All statistics reported are outlined in detail in Supplementary Tables 3 and 4.
