Magnitude of the late positive potential (LPP) at Cz in response to cigarette-related (CIG), pleasant (PLE), neutral (NEU), and unpleasant (UNP) pictures in young smokers who were classified into two groups using k-means cluster analysis. For Group 1, n = 20. For Group 2, n = 25. * = p < .05 for the within-group difference between cigarette-related and pleasant pictures (Bonferroni-corrected for all pairwise comparisons).