Chapter 14 explores how our personalities are shaped. There were several twin and adoption studies highlighted, that were conducted at the University of Minnesota. Those studies explored the role environment has on personalities. There are also numerous molecular genetic studies conducted to learn more about how our genes are related to our personality.
I found Sigmund Freud's psychoanalytic theory of personality particularly interesting. He traces much of our thoughts and behaviors back to sexual drive and aggression. He structures personality into three different components: Id, Ego, and Superego. Id is completely unconscious and where our basic instincts and impulses, including sex and aggression, are generated. It strives for immediate gratification. The Ego is the boss of the personality. It is governed by the reality principle: strives to delay gratification until it can find an appropriate outlet. It interacts with the real world to find ways to resolve competing demands of the other to psychic agencies. Our Superego gives us our sense of morality. It helps us establish right from wrong from our interactions with society.
The text also introduced graphology (psychological interpretation of handwriting) as a way to foreshadow certain characteristics of a person.
Most researchers have failed to uncover strong or consistent associations between birth order and personality; however, I have always been intrigued with the possibility that there is. There is a common belief that first borns are said to strive towards achievement. Middle borns seek diplomacy. And later borns are said to be the risk takers.
This video elaborates on the possibility of associations between birth order and personality: