Rats were classified as goal-trackers (GTs; n = 11), intermediate responders (IRs; n = 6), or sign-trackers (STs; n = 7) based on their average Pavlovian conditioned approach index scores during Sessions 4 and 5. (A) GTs, IRs, and STs did not differ in their levels of granulated (inactive) mast cells. (B) Compared with GTs and IRs, however, STs had more degranulated (active) mast cells. Anterior-posterior (AP) coordinates are measured from bregma. Data are presented as mean and S.E.M. ** - p < 0.01.