Is childhood lying shaped by callous-unemotional traits or does lie-telling make children more callous-unemotional? A longitudinal between- and within-person perspective.

The current study aims to advance knowledge on the causal interrelationship between childhood CU traits and lying both at a between- and a within-person perspective across a significant developmental period of mid-childhood to mid-adolescence. Cross-lagged panel models and Random-intercept cross-lagged panel models were used to investigate the prospective associations between lying and the distinct subcomponents of CU traits, including Callousness, Uncaring, and Unemotional in a sample of 719 children (T1; Mage  = 10.73 years, SDage  = 1.38, range = 7-15 years, 54.4% girls) across four assessment points. Results supported large vulnerability effects at the between-person level across time, indicating that CU traits predominantly influence the subsequent development of lying, with Callousness and Uncaring showing most profound effects on subsequent developmental processes of lying. At the within-person level, fluctuations in CU traits and lying were overall meaningfully related, but no causal relationship could be empirically determined. These findings provide a differentiated etiological viewpoint on the intertwinement of CU traits and lying at a young age, and underscore the importance of an early identification of children with callous and uncaring tendencies in order to prevent more persistent lying in adolescence.