1. Weaver et al propose that among rats, maternal behavior towards newborn pups influences their cortisol response to stress via epigenetic mechanisms that change the expression of glucocorticoid receptor gene for the rest of the pup’s life. They argue that because epigenetic patterns are established at specific developmental periods, there is extreme time sensitivity to when the pup is exposed to particular maternal behaviors (licking and grooming, in this case), and maternal behavior before or after that sensitive period window is not as important. Do you think this mechanism is relevant in humans? If so, what behaviors are most analogous to “maternal licking and grooming”?
Yes, I believe this could be relevant to humans. The concept of a "critical window" has been described in human studies. This concept has been applied in many developmental studies. For example, there is a critical window during development of the human urethra where the development is sensitive to hormones and after this time androgens/estrogens do not affect risk of hypospadias. In terms of behavior, the first concept that comes to my mind that reminds me of "maternal licking and grooming" is skin-on-skin contact immediately after birth or even breastfeeding in general. Ferber et al 2004 did an RCT of skin-to-skin contact after birth and found that those babies slept better, were more calm, and had better posturing that represented "better transitioning" to life outside of the womb.
http://pediatrics.aappublications.org/content/113/4/858.short
2. Gruenewald, in contrast, emphasize the cumulative effects of SES adversity on a multi-system allostatic load measure. Do you think that the Gruenewald findings are consistent, inconsistent, or unrelated to the Weaver findings? Explain.
I think these findings are consistent with the Weaver findings. In fact, I'm sure it is a mixture of both (one time exposure during a critical window versus multiple exposures during a less important window). As we age from childhood, we definitely become more resilient to stress in some ways (i.e. we've learned more about ourselves and society) but even when we are older there is still only so much stress that one can deal with.
3. Hertzmann and Boyce argue that “it is not genes or environment, nor is it genes and environment, but rather it is gene-by-environment interactions that influence developmental trajectories.” To what extent do you think that GxE interactions can contribute to major disparities along racial/ethnic, socioeconomic, or geographic dimensions?
This paradigm reminds me a lot of the cycle of poverty. In some sense your genes affect your behavior and then your behavior then affects your genes. There are many examples that we see along racial/ethnic/SES lines, for example, access to quality education. Hertzmann and Boyce discuss this cycle in the conclusions when they state that less privileged individuals will be more likely to be in situations of risk and privileged individuals will be more likely to be in protective environments. According to this research and theory, the biggest way to disrupt the cycle would be early childhood experiences but what about everyone else who are beyond childhood?