Fig. 3.

Social preference mother-infant reunion as a function of the OPRM1 C77G genotype (C/C, ■, or C/G, ▴). Values are given as the average duration of time that an infant spent in social contact with its mother or with other members of the social group (sec ± SEM) in a 300-sec scoring session during each of four reunion cycles (R1–R4). (A) Social Contact-Mother: 77G allele carriers had a different course of behavior over separation cycles than did 77C homozygotes [n = 26 vs. 64; OPRM1 genotype x time interaction, F(3,252) = 3.2, P = 0.02]. The interaction of OPRM1 genotype with time accounted for 5.6% of the variance in this behavior. (B) Social Contact-Other: Among carriers of the G allele, there was a decrease in the amount of time spent with other group members over repeated separation–reunion cycles [F(3,243) = 3, P = 0.03].