Personality

Personality...the ultimate marriage between genetics and environment. What of a personality is nature? What of a personality is nurture?

Then, the big question: IS OR ARE THERE A PERSONALITY GENE OR GENES!?!?!

Answers to this question could have major reprecussions. Is a person who is aggresive aggresive because they choose to be, or because their genes do not allow them to be another way? Should we punish people for aggresive behavior if they are genetically prone to it? Etc. Etc.

The Adventure Begins...

I would like you to first consider the domestication of foxes.

media type="youtube" key="AAV6ywEDfNE" height="315" width="420"

As you can see, personality traits can be bred into living beings, like friendliness towards humans was bred into these foxes. This indicates that at least part of personality is innate, or controlled by genetics.

But where is the evidence?

Ridley invited us to consider a gene on chromosome 11: the D4DR gene. The gene determines whether a neuron is part of the brain's dopamine pathway. Dopamine is a neurotransmitter that, as one of many functions, controls bloodflow to the brain. In connection to personality, "A shortage of dopamine in the brain causes an indecisive and frozen personality, unable to initiate even the body's own movement. In the extreme form, this is know as Parkinson's disease...In human beings, excessive dopamine may be the immediate cause of schizophrenia..." (162). So, somehow, differences in the genetics as related to the D4DR gene cause extreme differences from the norm like Parkinson's and schizophrenia.



Dopamine in the day to day personality is associated with novelty-seeking behaviors. There are two categories of the D4DR gene: long and short. Longer ones have more repeates of a phrase in the middle of the gene and shorter have fewer copies. After multiple studies were done it was conculded that, "People with 'long' D4DR genes have low responsiveness to dopamine, so they need to take a more adventerous approach to life to get the same dopamine 'buzz' that short-gened people get from simple things. In search of theses buzzes they develope novelty-seeking personalities" (164).

So, as far as that one snippet of personality goes there may be a genetic explanation behind the spectrum from creature of habit to bold adventurer.

media type="youtube" key="GGphGbJool4" height="315" width="420"

I'm betting he has a longer version of the gene...

But alas, we all know much more comes into play when it comes to personality that just the genes.

For example, shyness. In the book it was mentioned that, "when a naturally shy baby monkies are fostered to confident monkey mothers, they quickly outgrow their shyness." (165). So, what this means is that we all are predisoposed to have certain personality traits. However, outside forces, such as parenting, can change whether or how these traits are expressed. Ridley put it, "Mood, mind, personality and behaviour are indeed socially determined, but that does not mean they are not also biologically determined. Social influences upon behaviour work through the switching on and off of genes." (172). Genes make the chemicals that control our brains...and our brains are what make our personalities. What genes get activitated is due largely to surroundings. So, the genetics of personality is nowhere near absolute.

The quest continues...

Hi Rebecca! Although most believe that "nurture" has a greater impact on the development of one's personality, your module exemplified the importance of "nature," or rather, the two categories of D4DR genes in humans, on personality development. It is interesting that the amount of dopamine produced by either the long D4DR or short D4DR can determine either a genetic personality disorder, or the broad spectrum of various personalities, from shy to "stunt junkies" as your second clip referred to these daredevils. I suppose that I have a shorter version of the D4DR gene, as I have a far greater sense of my own mortality than these stuntmen (I even hate the climbing unit in Outdoor Adventure...). Great work! ~Shana

Hey Rebecca, You do a great job of summarizing the effects of the gene D4DR on personality. It was very interesting to learn the connection between dopamine produced and how long or short the D4DR gene is. The video of fox domestication proved your point well, that part of personality is innate. The fact that the breeders achieved in breeding domesticated foxes in just 50 years is incredible. I was surprised to find that they did it by breeding the foxes that were most friendly to humans together. One would usually think that it would be a strange and useless method, but the breeders' sucess prove otherwise. Overall you achieve a balance between showing the innate side of personality and the part that is influenced by the environment. And we see that personality, as with other things, is both a result of nature and nurture. -Boyi