Thanks for the comments Benjamin. I believe Weaver et al would expect the associations they observe to play out at a population level, even if they are evaluating small numbers of individual animals. Population patterns are amalgamations of individual experiences so if we see biological embedding of maternal behaviors for individuals, we should see if for the population (barring odd confounding structures). The key Weuver Gruenewald distinction is about the timing of exposure: is there a special importance of very early life or are there cumulative consequences of lifelong exposures?
Maria