Week of Sept 23rd-27th: Nature vs. Nurture
Is Aggression due to Nature or Nurture? (Debate Papers due in Brightspace “Assignments” Oct 7th-
11th)
Nature:
Article 1:
Lacourse et al. (2014). A longitudinal twin study of physical aggression during early childhood: evidence
for a developmentally dynamic genome. Psychological Medicine, 44(12), 2617-2627.
Abstract:
Background
Physical aggression (PA) tends to have its onset in infancy and to increase rapidly in frequency. Very little
is known about the genetic and environmental etiology of PA development during early childhood. We
investigated the temporal pattern of genetic and environmental etiology of PA during this crucial
developmental period.
Method
Participants were 667 twin pairs, including 254 monozygotic and 413 dizygotic pairs, from the ongoing
longitudinal Quebec Newborn Twin Study. Maternal reports of PA were obtained from three waves of
data at 20, 32 and 50 months. These reports were analysed using a biometric Cholesky decomposition and
linear latent growth curve model.
Results
The best-fitting Cholesky model revealed developmentally dynamic effects, mostly genetic attenuation
and innovation. The contribution of genetic factors at 20 months substantially decreased over time, while
new genetic effects appeared later on. The linear latent growth curve model revealed a significant
moderate increase in PA from 20 to 50 months. Two separate sets of uncorrelated genetic factors
accounted for the variation in initial level and growth rate. Non-shared and shared environments had no
effect on the stability, initial status and growth rate in PA.
Conclusions
Genetic factors underlie PA frequency and stability during early childhood; they are also responsible for
initial status and growth rate in PA. The contribution of shared environment is modest, and perhaps
limited, as it appears only at 50 months. Future research should investigate the complex nature of these
dynamic genetic factors through genetic–environment correlation (rGE) and interaction (G × E) analyses.
Is Aggression due to Nature or Nurture? (Debate Papers due in Brightspace “Assignments” Oct 7th-
11th)
Nature:
Article 1:
Lacourse et al. (2014). A longitudinal twin study of physical aggression during early childhood: evidence
for a developmentally dynamic genome. Psychological Medicine, 44(12), 2617-2627.
Abstract:
Background
Physical aggression (PA) tends to have its onset in infancy and to increase rapidly in frequency. Very little
is known about the genetic and environmental etiology of PA development during early childhood. We
investigated the temporal pattern of genetic and environmental etiology of PA during this crucial
developmental period.
Method
Participants were 667 twin pairs, including 254 monozygotic and 413 dizygotic pairs, from the ongoing
longitudinal Quebec Newborn Twin Study. Maternal reports of PA were obtained from three waves of
data at 20, 32 and 50 months. These reports were analysed using a biometric Cholesky decomposition and
linear latent growth curve model.
Results
The best-fitting Cholesky model revealed developmentally dynamic effects, mostly genetic attenuation
and innovation. The contribution of genetic factors at 20 months substantially decreased over time, while
new genetic effects appeared later on. The linear latent growth curve model revealed a significant
moderate increase in PA from 20 to 50 months. Two separate sets of uncorrelated genetic factors
accounted for the variation in initial level and growth rate. Non-shared and shared environments had no
effect on the stability, initial status and growth rate in PA.
Conclusions
Genetic factors underlie PA frequency and stability during early childhood; they are also responsible for
initial status and growth rate in PA. The contribution of shared environment is modest, and perhaps
limited, as it appears only at 50 months. Future research should investigate the complex nature of these
dynamic genetic factors through genetic–environment correlation (rGE) and interaction (G × E) analyses.
