(A-C) One cohort of mice was assessed with the social approach test at young (A) and old (B) age and another cohort of mice at middle age (C). Mice were placed individually into the empty center chamber of a three-chamber apparatus. One side-chamber contained an empty cup, and the other an identical cup with an unfamiliar live mouse in it. Close contact with each cup was monitored for 10 min. n = 12 (A, B) or 17 (C) NTG; 13 (A) or 10 (B) TRE-hTau-A152T(L1); 12 (A), 9 (B), or 12 (C) CamKII-tTA; 13 (C) hTau-WT(L32); and 14 (A), 12 (B), or 10 (C) hTau-A152T(L1) mice. *P < 0.05, **P < 0.01, ***P < 0.001 by one-tailed paired t test with Holm adjustment. Values are means ± SEM. 