Rat dams can be divided based on their maternal care into high, mid, or low licking/grooming (LG) mothers. The pups raised by low LG mothers have less glucocorticoid receptor (GR) mRNA brought about by GR gene methylation. Consequently, the offspring of low-LG mothers have higher anxiety and impaired learning when adults. Because it is elicited by maternal behavior, such methylation is maintained across generations. However, upon cross-fostering (change of low LG mother to high LG mother) the methylation level of the GR promoter is restored. What does this result imply?