“…By contrast, a subpopulation of rats maintained their seeking response despite punishment, thereby displaying compulsive alcohol seeking behavior (Figure 2a and b). A cluster analysis (Tye et al, 2010;Murray et al, 2015;Engeln et al, 2016) performed on the completed seeking-taking cycles during the last 3 sessions of punishment (Supplementary Figure S3) confirmed the existence of three subgroups of rats: 34% of the population displayed compulsive alcohol seeking (compulsive, C, rats, n = 21), whereas, unexpectedly, a 30% sub-population greatly suppressed their seeking responses (NC rats, n = 18); 36% of the population (intermediate, I, rats, n = 22) between C and NC rats partially suppressed seeking when intermittently punished (compulsivity: F 2,55 = 84.55, po0.001, η 2 = 0.75 and time × compulsivity: F 18,495 = 16.75, po0.001, η 2 = 0.38). These data demonstrate that the propensity to drink alcohol is clearly not sufficient to predict the transition to compulsive alcohol seeking behavior (see SOM).…”