All human traits and personality characteristics, from our height to our fear of heights, are driven by a complex interplay between the expression of our genes and the feedback from our environment. We now know that the lion's share of human genes are expressed in the brain and that almost all normal and disordered behaviors are polygenic, meaning that they are each influenced by a large number of genes. Scientists are therefore tasked with a massive but increasingly plausible mission: mapping the pathway from our genes to the person we see in the mirror.
Our Genes, Our Environment, and Us
Genes and experiences both help to define who an individual is: one’s personality traits, intelligence, propensity to struggle with a mental illness, and other psychological qualities, in addition to all of the physical ones. But what scientists have learned about how these influences play out can clash with common wisdom. A trait that appears to result from a child’s upbringing may actually be largely a product of the genes she inherited from her parents, who share those genes with her. In fact, research investigating the influence of the family environment has found that, generally speaking, it accounts for a surprisingly little amount of the differences between people on the characteristics that scientists measure.