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. Author manuscript; available in PMC: 2016 May 15.
Published in final edited form as: Biol Psychiatry. 2014 Nov 7;77(10):887–894. doi: 10.1016/j.biopsych.2014.10.022

Table 2.

Longitudinal cross-age genetic and environmental correlations for delay discounting measures.

DD Measure Genetic and environmental
correlations		 Proportions of cross-age covariance
attributable to
rG (16–18) rE (16–18) A E
AUC 1.0 .29 (.05 – .49) .80 (.61 – .97) .20 (.03 – .39)
log k 1.0 .25 (.03 – .45) .76 (.53 – .97) .24 (.03 – .47)
AUC (Ex) 1.0 .53 (.25 – .73) .65 (.41 – .85) .35 (.15 – .59)
log k (Ex) 1.0 .51 (.22 – .74) .56 (.27 – .82) .44 (.18 – .73)

rG = genetic correlation which is equal to 1.00 because only one genetic factor operating at both ages was retained in the final model, while additional age-specific genetic factors could be dropped without significant deterioration of model fit; rE=non-shared environmental correlation. rG and rE show the extent of the overlap between genetic and environmental influences, respectively, on the DD measures at ages 16 and 18. The last two columns show what proportion of cross-age correlation (i.e. longitudinal stability) can be attributed to genetic or environmental factors operating at both ages. Confidence intervals (95%) are shown in brackets.