There is another book that has been really interesting on a personal level and in dealing with my husband. It is called Why Him? Why Her? by Helen Fisher, Ph.D. She has based a lot of her research on Dr. Keirsey's work and a lot of the same resources as him. Something very interesting in her research is the chemicals that are prominent in the different personality types. She has used different personality type names and so I'll put them next to my titles for the types.
The Helper- The Builder: Serotonin's Magic
The Helper traits of loyalty, conscientiousness, duty, respectability, making plans, social, cautious, etc. come from Serotonin.
"Serotonin has extensive highways through the brain. You inherit your basic activities of this chemical...And this chemical floods, lingers, and recedes from various brain regions, it affects our attitudes and behavior. No brain system acts alone, of course. Serotonin, for instance, can elevate estrogen levels in the brain regions that influence thinking, emotion and memory. Serotonin can also trigger the release of oxytocin- a chemical associated with trusting and the ability to figure out others' states of mind. So all three of these chemicals probably contribute to the Builder's affability, their deep need to attach to family and community, and their tact and managerial skills.
Moreover, serotonin can suppress testosterone activity, particularly in a brain center associated with fear, anger and aggression- the amygdala. The may be why, in part, Builders tend to be calm and self- confident: their serotonin is suppressing aggressive tendencies. Last serotonin suppresses dopamine activity. And as you recall, dopamine often produces impulsive recklessness; hence it is likely that by reducing dopamine activity, serotonin generates the Builder's caution." (Fisher, pg. 64-66)
The Player- The Explorer: Dopamine: The Chemistry of Sensation Seeking
This type is the kind that get easily excited and easily bored. In Dr. Fisher's study, she found that this type all agreed on the statement "I find unpredictable situations exhilarating."
"This sensation-seeking disposition is largely inherited. In fact, some of the contributing genes involved have been discovered. A gene labeled DRD4 controls much of the dopamine activity in brain regions used for thinking, feeling, and motivation. And a specific version of this gene is associated with several varieties of novelty seeking. Old or young; male or female; rich or poor; educated in the ivory tower or on the mean streets: people who have inherited this gene in the dopamine system have an appetite for variety.
Dopamine acts in tandem with several other chemicals, of course, including the closely related norepinephrine and lesser players such as testosterone and serotonin. " (Fisher, pg. 45)
The Feeler- The Negotiator: Estrogen: The Mother Lode
"How does estrogen enable Negotiators to do their web thinking?
With brain wiring. The brain's two hemispheres are connected by millions of nerve fibers, and individuals who were exposed to more estrogen in the womb have more connections between these brain halves. Estrogen also builds more nerve connections between these brain halves. Estrogen also builds more nerve connections between distant regions within each hemisphere. In short, fetal estrogen constructs a well-connected brain- contributing to the Negotiator's ability to collect and integrate a broad range of information." (Fisher, pg. 106)
"Puberty and life experiences also adjust estrogen activities, however, altering web thinking." (pg. 106) There is a study in her book showing people receiving estrogen and testosterone treatments. The one receiving estrogen remarked how they took longer to make decisions now and they needed to weigh options. The other who was receiving testosterone noticed that they started to miss the overall picture that they once used to take note of.
"Estrogen and testosterone can suppress or enhance each other, depending on many circumstances and interactions. But you inherit your basic levels of each." (pg. 106)
The Thinker- The Director: Testosterone Priming: Finger Talk
"Systemizing is linked with testosterone, and it's a skill you begin to acquire before you leave the womb.
As testosterone washes over the fetal brain, it builds the brain architecture for this systemizing ability. Meanwhile, surges of fetal estrogen begin to construct the brain anatomy for empathizing. Levels of both fetal testosterone and fetal estrogen swell and recede in patterns that are inherited. So, depending on the hand you're dealt, you will express predominantly testosterone, predominantly estrogen, or a lot or a little of both- thus predisposing you to be better at systemizing, at empathizing, or good or bad at both.
Testosterone leaves it's mark in many ways. Take a look at your right hand, palm up. The more testosterone you were exposed to in the womb, the longer your fourth or ring finger will be in relation to your second or pointing finger. If you were exposed to more estrogen, these two fingers will be the same length, or your pointing finger will be longer than your right finger.
Not all Directors receive a surge of testosterone in the womb, some have it at another time, probably puberty. So your finger might not be longer." (Fisher, pg. 86)
I hope you have found this information as interesting as I did! If you have any comments, please leave them below and don't forget to subscribe to the emails! Thanks for reading!
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