Onal) LC (C1 5) MLC (C6 10) MHC (C11 15) HC (C16 20) M 2.38 2.82 3.25 3.87 4.35 4.69 5.09 5.56 5.99 6.73 7.11 7.35 7.51 7.76 8.13 8.32 8.28 8.61 9.01 9.73 7.25 3.34 5.61 7.57 8.79 SD

Onal) LC (C1 5) MLC (C6 10) MHC (C11 15) HC (C16 20) M 2.38 2.82 3.25 3.87 4.35 4.69 5.09 5.56 5.99 6.73 7.11 7.35 7.51 7.76 8.13 8.32 8.28 8.61 9.01 9.73 7.25 3.34 5.61 7.57 8.79 SD 4.85 4.59 4.54 4.43 4.45 4.35 4.37 4.53 4.75 5.24 5.59 5.79 6.02 6.28 6.68 7.06 7.33 7.70 8.11 8.72 5.74 4.31 4.27 5.81 7.Results Simple StatisticsSome of the A-83-01 web participants required extensive help from the assistants to 181223-80-3 chemical information complete the control questions. Removing those 21 participants, data from 296 individuals were analyzed (209 females and 87 males, 213 MZ twins, 61 same sex DZ twins, and 22 opposite sex DZ twins). Age ranged from 18 to 37 years (M = 25.42, SD = 4.27). Mean conditional decisions increased in accordance with the investment by other group members (Table 1). We regressed sample mean decisions on others’ investment. The regression coefficient was positive and highly significant (b = 0.986, p < 0.001; R2 = 0.973, p < 0.001). This indicated that, on average, participants displayed a conditional cooperation strategy. We also observed that the variances (SD) of the decisions became larger as the contributions by others increased (i.e., C20 decision). The regression of SD on others' investment showed strong positive relationship (b = 0.921, p < 0.001; R2 = 0.849, p < 0.001). This showed that the degree of conditionality was not monotonic, especially when others were behaving cooperatively. In fact, 47 (15.8 ) participants did not change their investment through C1 20. These differences in the pattern contributed to the larger variances in the greater contribution settings.LC, lowest conditional; MLC, middle-low C; MHC, middle-high C; HC, highest Ccalculated four scores from the conditional decisions and subjected them to genetic analyses: lowest C (LC) scores (average of C1 to C5 decisions), middle-low C (MLC) scores (average of C6?C10), middle-high C (MHC) scores (average of C11 15), and highest C (HC) scores (average of C16 20). Table 2 shows the within-pair intraclass correlations for the four conditional scores and UC scores for MZ pairs and DZ pairs. The correlation coefficients were small even for MZ pairs, suggesting relatively small genetic influences. The differences between MZ pair correlations and DZ pair correlations were largest for the HC scores, which suggests that genetic influences were greater for decisions made in higher cooperativeness settings. To further analyze genetic and environmental influences, we conducted univariate genetic model-fitting analyses usingTABLE 2 | Within-pair intraclass correlations and 95 credible intervals for decision scores in Study 1. MZ UC LC MLC MHC HC 0.05 0.09 0.12 0.14 0.21 [0.15, [-0.11, [-0.08, [-0.06, [0.01, 95 CI 0.25] 0.28] 0.31] 0.33] 0.39] DZ -0.45 -0.07 0.15 0.07 0.02 95 CI [-0.69, [-0.41, [-0.22, [-0.29, [-0.34, -0.10] 0.30] 0.48] 0.42] 0.38]Genetic AnalysisWe conducted genetic analyses for 98 MZ pairs and 29 DZ pairs of which both co-twins had participated in the study. To qualitatively analyze the genetic and environmental influences, weMZ, monozygotic twin; DZ, dizygotic twin; CI, credible interval; UC, unconditional; LC, lowest conditional; MLC, middle-low C; MHC, middle-high C; HC, highest C.Frontiers in Psychology | www.frontiersin.orgApril 2015 | Volume 6 | ArticleHiraishi et al.Heritability of cooperative behaviorMarkov chain Monte Carlo (MCMC) algorithms (van den Berg et al., 2006). For each decision score, we constructed a Bayesian ACE model, in which the influences of additive.Onal) LC (C1 5) MLC (C6 10) MHC (C11 15) HC (C16 20) M 2.38 2.82 3.25 3.87 4.35 4.69 5.09 5.56 5.99 6.73 7.11 7.35 7.51 7.76 8.13 8.32 8.28 8.61 9.01 9.73 7.25 3.34 5.61 7.57 8.79 SD 4.85 4.59 4.54 4.43 4.45 4.35 4.37 4.53 4.75 5.24 5.59 5.79 6.02 6.28 6.68 7.06 7.33 7.70 8.11 8.72 5.74 4.31 4.27 5.81 7.Results Simple StatisticsSome of the participants required extensive help from the assistants to complete the control questions. Removing those 21 participants, data from 296 individuals were analyzed (209 females and 87 males, 213 MZ twins, 61 same sex DZ twins, and 22 opposite sex DZ twins). Age ranged from 18 to 37 years (M = 25.42, SD = 4.27). Mean conditional decisions increased in accordance with the investment by other group members (Table 1). We regressed sample mean decisions on others' investment. The regression coefficient was positive and highly significant (b = 0.986, p < 0.001; R2 = 0.973, p < 0.001). This indicated that, on average, participants displayed a conditional cooperation strategy. We also observed that the variances (SD) of the decisions became larger as the contributions by others increased (i.e., C20 decision). The regression of SD on others' investment showed strong positive relationship (b = 0.921, p < 0.001; R2 = 0.849, p < 0.001). This showed that the degree of conditionality was not monotonic, especially when others were behaving cooperatively. In fact, 47 (15.8 ) participants did not change their investment through C1 20. These differences in the pattern contributed to the larger variances in the greater contribution settings.LC, lowest conditional; MLC, middle-low C; MHC, middle-high C; HC, highest Ccalculated four scores from the conditional decisions and subjected them to genetic analyses: lowest C (LC) scores (average of C1 to C5 decisions), middle-low C (MLC) scores (average of C6?C10), middle-high C (MHC) scores (average of C11 15), and highest C (HC) scores (average of C16 20). Table 2 shows the within-pair intraclass correlations for the four conditional scores and UC scores for MZ pairs and DZ pairs. The correlation coefficients were small even for MZ pairs, suggesting relatively small genetic influences. The differences between MZ pair correlations and DZ pair correlations were largest for the HC scores, which suggests that genetic influences were greater for decisions made in higher cooperativeness settings. To further analyze genetic and environmental influences, we conducted univariate genetic model-fitting analyses usingTABLE 2 | Within-pair intraclass correlations and 95 credible intervals for decision scores in Study 1. MZ UC LC MLC MHC HC 0.05 0.09 0.12 0.14 0.21 [0.15, [-0.11, [-0.08, [-0.06, [0.01, 95 CI 0.25] 0.28] 0.31] 0.33] 0.39] DZ -0.45 -0.07 0.15 0.07 0.02 95 CI [-0.69, [-0.41, [-0.22, [-0.29, [-0.34, -0.10] 0.30] 0.48] 0.42] 0.38]Genetic AnalysisWe conducted genetic analyses for 98 MZ pairs and 29 DZ pairs of which both co-twins had participated in the study. To qualitatively analyze the genetic and environmental influences, weMZ, monozygotic twin; DZ, dizygotic twin; CI, credible interval; UC, unconditional; LC, lowest conditional; MLC, middle-low C; MHC, middle-high C; HC, highest C.Frontiers in Psychology | www.frontiersin.orgApril 2015 | Volume 6 | ArticleHiraishi et al.Heritability of cooperative behaviorMarkov chain Monte Carlo (MCMC) algorithms (van den Berg et al., 2006). For each decision score, we constructed a Bayesian ACE model, in which the influences of additive.