I wonder how would they ever exclude environmental factors? If children grow up in a house where the five-second rule never applies and hands are washed more routinely than most, wouldn't they be more likely to continue these patterns in the next generation?
Unless they can find more people like my DS...grew up in a family of clutterers, but now keeps an immaculate house with little "stuff" around. (Not bad....just different. We're each a little off-center; neither of us at extremes.)
Sue