Real-time social preference of C57BL/6J and Oprm1 mutant judges. A–C, C57BL/6J judges (n = 25) simultaneously engaging with social targets that are typical (Oprm1+/+) or atypical (Oprm1+/−), as shown in a schematic diagram (A), along with time spent in each chamber (B) and preference score (C). D–F, C57BL/6J judges (n = 23) simultaneously engaging with social targets that are typical (Oprm1+/+) or atypical (Oprm1−/−), as shown in a schematic diagram (D), along with time spent in each chamber (E) and preference score (F). G–I, Oprm1+/− judges (n = 8) simultaneously engaging with social targets that are typical (Oprm1+/+) or atypical (Oprm1−/−), as shown in a schematic diagram (G), along with time spent in each chamber (H) and preference score (I). J–L, Oprm1−/− judges (n = 13) simultaneously engaging with social targets that are typical (Oprm1+/+) or atypical (Oprm1−/−), as shown in a schematic diagram (J), along with time spent in each chamber (K) and preference score (L). All groups contained similar numbers of female mice (open symbols) and male mice (closed symbols). *p < 0.05 according to LSD post hoc test (E, K) or one-sample t test (F, L).