1 Appendix A: Moderating effect of winning/losing contest 2 3 Using forward stepwise regression, three separate moderator regression analyses 4 were performed with one of the behavioral indices as the dependent variable. The sex of 5 the stimulus person was dummy-coded as 0 for a man and 1 for a woman and the 6 outcome of the competition was dummy-coded as 0 for the losers and 1 for the winners. 7 For calculating the change in T during the competition we used the unstandardized 8 residuals from regressing T1 on T2. In Step 1, the main effects of Sex of the stimulus 9 person, the Outcome of the competition and the Change in T during the competition were 10 entered. In Step 2, the Sex × Change in T interaction and the Outcome × Change-in-T 11 interaction and the Sex × Outcome interaction were added. In step 3 the three way 12 interaction term Sex × Change in T interaction × Outcome was added. 13 14 Interest in the stimulus person 15 16 The model in step 1, including Sex of the stimulus person, Outcome of the 17 competition and the Change in T during the competition as predictor variables, did not 18 explain a significant amount of variance in the index of interest in the stimulus person 19 (F3,73 = 0.37, p = 0.778). However, entering the three two-way interaction terms in step 2 20 significantly increased the amount of variance explained (ΔF3,70 = 3.76, p = 0.015, 21 adjusted R² = 7.9%, ΔR² = 13.7%). In this step, the only significant effect was the 2-way 22 interaction between the change in T and sex (β = 0.336, p = 0.030). See the main 23 manuscript for significance tests of the slopes. In step 3, entering the interaction term Sex 1 24 × Change in T interaction × Outcome did not explain a significant amount of variance in 25 the index of interest in the stimulus person (ΔF1,69 = 0.46, p = 0.500). 26 27 Self-presentation 28 29 The model in step 1, including Sex of the stimulus person, Outcome of the 30 competition and the Change in T during the competition as predictor variables, did not 31 explain a significant amount of variance in the index of self-presentation (F3,73 = 0.16, p 32 = 0.925). However, entering the three two-way interaction terms in step 2 significantly 33 increased the amount of variance explained (ΔF3,70 = 2.86, p = 0.043, adjusted R² = 3.9%, 34 ΔR² = 10.9%). In this step, the only significant effect was the 2-way interaction between 35 the change in T and sex (β = 0.329, p = 0.037). See the main manuscript for significance 36 tests of the slopes. In step 3, entering the interaction term Sex × Change in T interaction × 37 Outcome did not explain a significant amount of variance in the index of self-presentation 38 (ΔF1,69 = 0.35, p = 0.558). 39 2 40 Positive facial cues 41 42 The model in step 1, including Sex of the stimulus person, Outcome of the 43 competition and the Change in T during the competition as predictor variables, explained 44 a significant amount of variance in positive facial cues (ΔF3,73 = 2.87, p = 0.042, adjusted 45 R² = 6.9%, ΔR² = 10.5%). In this step, the only significant effect was the main effect of T 46 change (β = 0.276, p = 0.017). Additionally, entering the three two-way interaction terms 47 in step 2 did not increase the amount of variance explained (ΔF3,70 = 2.00, p = 0.122). In 48 step 3, entering the interaction term Sex × Change in T interaction × Outcome did not 49 explain a significant amount of variance in the index of positive facial cues (ΔF1,69 = 50 0.12, p = 0.736). 51 3 52 Appendix B: Effects of baseline T 53 54 Using forward stepwise regression, three separate moderator regression 55 analyses were performed with one of the behavioral indices as the dependent variable. 56 The sex of the stimulus person was dummy-coded as 0 for a man and 1 for a woman and 57 the outcome of the competition was dummy-coded as 0 for the losers and 1 for the 58 winners. In Step 1, the main effects of Sex of the stimulus person, the Outcome of the 59 competition and Baseline T were entered. In Step 2, the Sex × Baseline T interaction, the 60 Outcome × Baseline T interaction, and the Sex × Outcome interaction were added. In step 61 3 the three way interaction term Sex × Baseline T × Outcome interaction was added. 62 63 Interest in the stimulus person 64 65 The model in step 1, including Sex of the stimulus person, Outcome of the 66 competition and Baseline T as predictor variables, did not explain a significant amount of 67 variance in the of interest in the stimulus person (F3,73 = 0.85, p = 0.968). Entering the 68 three two-way interaction terms in step 2 did not significantly increase the amount of 69 variance explained (ΔF3,70 = 0.47, p = 0.707). In step 3, entering the interaction term Sex 70 × Baseline T × Outcome did not explain a significant amount of variance in the index of 71 interest in the stimulus person (ΔF1,69 = 0.70, p = 0.407). 72 4 73 Self presentation 74 75 The model in step 1, including Sex of the stimulus person, Outcome of the 76 competition and Baseline T as predictor variables, did not explain a significant amount of 77 variance in the index self presentation (F3,73 = 0.21, p = 0.886). Entering the three two- 78 way interaction terms in step 2 did not significantly increase the amount of variance 79 explained (ΔF3,70 = 0.04, p = 0.988). In step 3, entering the interaction term Sex × 80 Baseline T × Outcome did not explain a significant amount of variance in the index self 81 presentation (ΔF1,69 = 0.34, p = 0.565). 82 83 Positive facial cues 84 85 The model in step 1, including Sex of the stimulus person, Outcome of the 86 competition and Baseline T as predictor variables, did not explain a significant amount of 87 variance in the index positive facial cues (F3,73 = 0.90, p = 0.446). Entering the three two- 88 way interaction terms in step 2 did not significantly increase the amount of variance 89 explained (ΔF3,70 = 0.43, p = 0.730). In step 3, entering the interaction term Sex × 90 Baseline T × Outcome did not explain a significant amount of variance in the index self 91 presentation (ΔF1,69 = 1.71, p = 0.195). 92 5 93 Appendix C: Controlling for the opponent’s psychological state (see ref. [20]) 94 95 Using forward stepwise regression, three separate moderator regression analyses 96 were performed with one of the behavioural indices as the dependent variable. The sex of 97 the stimulus person was dummy-coded as 0 for a man and 1 for a woman. For calculating 98 the change in T during the competition we used the unstandardized residuals from 99 regressing T1 on T2. In Step 1, the main effects of Sex of the stimulus person, and the 100 Change in T during the competition were entered. Additionally, as a control we added in 101 Step 1 the opponents’ self-reported self-efficacy, perceived importance of the 102 competition, and expectancy to win or lose. In Step 2, the Sex × Change in T interaction 103 was added. 104 105 Interest in the stimulus person 106 107 The model in step 1 included the following predictor variables: (i) Sex of the 108 stimulus person, (ii) Change in T during the competition, (iii) Opponents’ self-reported 109 self-efficacy, (iv) Opponents’ perceived importance of the competition, and (v) 110 Opponents’ expectancy to win or lose. This model did not explain a significant amount of 111 variance in the index of interest in the stimulus person (F5,71 = 1.88, p = 0.109). However, 112 entering the interaction terms in step 2 marginally increased the amount of variance 113 explained (ΔF1,70 = 3.85, p = 0.054, adjusted R² = 9.1%, ΔR² = 4.6%). See the main 114 manuscript for significance tests of the slopes. 115 6 116 Self-presentation 117 118 The model in step 1 included the following predictor variables: (i) Sex of the 119 stimulus person, (ii) Change in T during the competition, (iii) Opponents’ self-reported 120 self-efficacy, (iv) Opponents’ perceived importance of the competition, and (v) 121 Opponents’ expectancy to win or lose. This model did not explain a significant amount of 122 variance in the index of self-presentation (F5,71 = 0.80, p = 0.553). However, entering the 123 interaction terms in step 2 significantly increased the amount of variance explained 124 (ΔF1,70 = 5.29, p = 0.024, adjusted R² = 4.4%, ΔR² = 6.7%). %). See the main manuscript 125 for significance tests of the slopes. 126 127 Positive facial cues 128 129 The model in step 1 included the following predictor variables: (i) Sex of the 130 stimulus person, (ii) Change in T during the competition, (iii) Opponents’ self-reported 131 self-efficacy, (iv) Opponents’ perceived importance of the competition, and (v) 132 Opponents’ expectancy to win or lose. This model explained a significant amount of the 133 variance in positive facial cues (ΔF5,71 = 4.16, p = 0.002, adjusted R² = 17.2%, R² = 134 22.7%). Entering the interaction term in step 2 did not increase the amount of variance 135 explained (ΔF1,70 = 2.05, p = 0.156). 7 136 Appendix D: Regression analysis with only one factor (overall affiliative behaviour) 137 138 We averaged the scores from all nine items to create one composite factor, which 139 we term overall affiliative behaviour. The factor loadings for this variable were as 140 follows: 141 142 Table 1. Factor loading of the behavioral items on only one factor 143 Nº Behavioral item Loading 1 -Gave attention to stimulus person 0.954 2 -Showed interest in stimulus person 0.971 3 -Interacted confidently with stimulus person 0.945 4 -Asked questions 0.866 5 -Was talkative 0.925 6 -Talked about himself 0.864 7 -Revealed details about himself 0.817 8 -Was smiling 0.650 9 -Made eye contact 0.865 144 145 The model in step 1, including sex of the stimulus person and the change in T 146 during the competition as predictor variables, did not explain a significant amount of 147 variance in overall affiliative behaviour (F2,74 = 0.77, p = 0.469). However, entering the 8 148 interaction term in step 2 significantly increased the amount of variance explained (ΔF1,73 149 = 5.68, p = 0.020, adjusted R² = 5.4%, ΔR² = 7.1%). In this step, there were no main 150 effects of sex of the stimulus person (p = 0.737) or change in T (p = 0.525), but there was 151 a significant 2-way interaction between the change in T and sex (β = 0.356, p = 0.020). 152 Significance tests of the slopes revealed that while the change in T did not affect overall 153 affiliative behaviour when interacting with a man (t73 = -0.639, β = -0.096, p = 0.525), a 154 greater change in T was associated with a higher score for overall affiliative behaviour 155 when interacting with a woman (t73 = 2.62, β = 0.443, p = 0.011). 9