A topic from "Behave" that I have been perusing is gene-environment interactions, a topic strongly related to the age old debate of nature vs. nurture. How pivotal of a role do our genes play in explaining human behavior and preferences? How much do my genes determine my strong love for pancakes?
There are two terms here that Sapolsky defines and, as he admits, are highly unintuitive:
If genes strongly influence average levels of a trait, that trait is strongly inherited. If genes strongly influence the extent of variability around that average level, that trait has high heritability.Sapolsky gives the example of height variation in a plant species with three gene versions. Version A will grow to be 1 inch tall, B to be 2 inches tall, and C to be 3 inches tall. In this scenario, the differences in height is completely determined by genes, and is thus 100% heritable. However, consider that this plant species always has leaves at the base closest to the roots, with an occasional anomaly of a plant with leaves at the top near the flowers. The trait of low-lying leaves would be highly inherited with low heritability; the genes predict the placement of leaves and don't explain the anomalous difference of leaves growing at the top of the plant.
So what drives differences, and how much of it is actually driven by genetics? I found Sapolsky's point about environment crucial: if you only study the gene in a particular environment, you fail to observe how the gene works in other environments. As expected, genes work differently in different environments. Furthermore, studying the gene in multiple environments decreases the influence of heritability, and suddenly the influence of genes on plant height is less due to genes and more influenced by environment. The actual heritability of a trait is highly context-dependent. Imagine the intricacies of studying human behavior in the context of environment, where there are infinite types of living environments, lifestyles, and traumas.
Related to gene-environment interaction is a topic that I took more personally: collectivist vs. individualist culture (or East Asian and American cultures, respectively). There are three scenarios in the book, which I used to "determine" how "Asian" and "American" I am:
1) Americans are more likely to remember when they influenced someone, while East Asians will remember times when someone influenced them.
I'm 50-50. I have strong admiration and memories of mentors who have had significant impact on my decisions for my career and path forward, but I have equally strong memories of times when friends and acquaintances would remark on something I did to help them through challenges.
2) Which two go together? A monkey, a bear, and a banana.
I instinctively said monkey and banana, associating a monkey with eating a banana. According to research, the cultural differences cause Americans to process this situation categorically; the monkey and bear go together since they are animals. East Asians, however, think about the relationship between a monkey and a banana; the monkey will need to eat the banana to nourish its body and survive.
3) When looking at a picture, what do you notice first? The scene or the person in the middle?
I tend to notice the person in the middle of a scene. Generally, Americans will look towards the center of the photo first, while East Asians look holistically at the entire photo.
What I found utterly fascinating is the environmental and ecological influence of rice on collectivism. Rice is the staple of East Asian food, and its harvesting requires extensive cooperation beyond family boundaries to successfully build and maintain rice irrigation systems. Rice harvesting is not a solitary activity. And on the topic of heritability and environment: a gene variant responsible for extroversion and impulsive activity occurs in 23% of Europeans and European Americans, but only 1% in East Asians. Collectivist rice farming societies trended against this variant as rice domestication progressed.
I couldn't help but think about my parents and how their actions strongly reflect collectivism. My mother makes lunch for my father every single day, and it is almost the exact same lunch: romaine lettuce with tomatoes, avocado, mushroom, many other vegetables, an egg, with bagel and oatmeal on the side. She always said it was natural for her to do so and she never had to think twice about putting together a meal for him. My father never complains about the meal, despite it almost being the exact same lunch every day.* I assume this is part of his "collectivist mindset", where he understands that every person contributes to the overall well-being of the family in some way. In turn, he does a lot of the cleaning in the house and likes to maintain garden and plants in the yard, keeping our family's living space clean.
My parents do all that without consciously dividing up tasks. To me, it seems like they naturally fell into those roles because they were aware of the individual contribution needed to create a healthy, communal environment for the family.
Genes, environment, and culture - the interplay among these three must somehow create a unique blueprint for every individual's behavior.
* If it were me, I might have resorted to making my own lunches because the individualist in me wants to take charge of my meals and have something other than nutritious, healthy salads daily.
