Discomfort 28.30 27.69 9.77 72.02 1.23 0.039 0.033 0.174** * 0.139 1.149** * 0.417 0.477 0.167 Fear 19.12 18.89 8.31 60.61 0.00 0.009 0.008 0.093 0.081 0.811** * 0.320 0.427 0.162 Frustration 8.06 7.99 8.91 0.00 0.00 0.019 0.017 0.122 0.105 0.088 0.034 0.157 0.059 Sadness 6.98 6.81 4.23 40.43 0.00 0.043 0.039 0.140 0.123 0.454 0.181 0.002 0.001 Shyness 3.99 3.92 3.13 20.59 0.00 0.006 0.005 0.012 0.009 0.347 0.123 0.017 0.006 Motor activity 11.53 12.88 11.34 14.52 0.95 0.022 0.024 0.145** * 0.151 0.339 0.161 0.235 0.107 Perceptual sensitivity 13.45 12.72 6.03 56.20 0.11 0.165** * 0.119 0.086 0.059 0.833** * 0.262 0.348 0.105 Soothability 12.14 11.79 5.80 54.22 0.00 0.057 0.051 0.088 0.076 0.683** * 0.267 0.193 0.073

Effortful control 3.23 3.45 2.51 33.33 1.22 0.123** * 0.177 0.001 0.001 0.094 0.059 0.161 0.097 Attention focusing 1.67 1.37 0.46 33.33 0.00 0.065 0.058 0.014 0.012 0.260 0.100 0.098 0.036 Attention shifting 6.53 6.42 3.95 42.31 0.00 0.050 0.059 0.039 0.044 0.016 0.008 0.341 0.168 Cuddliness 8.03 8.06 7.04 13.27 0.00 0.146** * 0.137 0.023 0.021 0.289 0.118 0.203 0.080 Inhibition 7.89 8.58 9.95 0.00 0.00 0.124 0.101 0.027 0.021 0.006 0.002 0.109 0.037

Low-intensity pleasure 6.74 6.94 4.43 40.00 4.69 0.234*** 0.234 0.028 0.027 0.411 0.178 0.106 0.044 1Between-culture variance (R2 Between) reflects reduction in between-level variance attributed to sleep practices while controlling for age and gender covariates. 2Within-culture variance (R2 Within) reflects reduction in within-level variance attributed to sleep practices while controlling for age and gender covariates. , unstandardized coefficient; , standardized coefficient; and ICC, interclass correlation. ***p < 0.001. Model 1 reflects ICC for models with age and gender covariates. Model 2 reflects the ICC after including sleep practices.

Rank-ordering the extent to which a cultures sample endorsed using passive techniques (Supplementary Figure 1), we find that the United States, Finland, and Netherlands top the list and South Korea, Turkey, and China are at the bottom of this distribution. In contrast, rank-ordering for active techniques (Supplementary Figure 2), we find that Romania, Spain, and Chile top the list while Turkey, Italy, and Belgium are at the bottom of the distribution. contributions to cross-cultural differences in child temperament. Overall, passive sleep-supporting techniques (e.g., cuddling) were associated with temperament outcomes at the culture level (e.g., higher levels of sociability, lower NE) and at the individual level (e.g., higher levels of EC), whereas active sleep-supporting techniques (e.g., doing an activity together) were associated with temperament outcomes at an individual level only (e.g., higher NE), largely supporting hypotheses.