Mice trained to associate an auditory cue with an aversive stimulus were placed in a masked context for 3 min prior to a 3 min exposure to the conditioned cue. Fearful behaviour (freezing) was measured in adult male (A) and female (B) offspring of dams that received either saline (solid symbols) or CBX (open symbols) along with either water (squares) or the antioxidant tempol (circles) during pregnancy. n = 13 male saline, n = 10 male CBX, n = 6 male saline–tempol, n = 6 male CBX–tempol, n = 14 female saline, n = 5 female CBX, n = 5 female saline–tempol, n = 4 female CBX–tempol; †P < 0.01 tempol compared with no tempol.