Theories of Personality (PSY 225-A01)/Chapter 5

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Genetic Effects[edit | edit source]

  • Darwinian concepts - Natural selection ("survival of the fittest" --> adaptive genes pass on; extent it plays in humans?); Functionalism (role of those genes play in the environment? What is the function of intelligence vs the color of the moth's wings in order to blend in with its environment? Is aggression/agreement an adaptive gene?).

Genetic disorders play a role in personality, such as Williams syndrome. Genetic disorders are associated with personality patterns. Genetics can affect one's personality.

Behavioral genomics is studying how genes affect behavior. How genes function together and the environment in order to influence the outcome. Behavioral genetics is looking at how individual biological differences impact behavior.

Bottom-line question: How our genes affect our behavior?

Temperament[edit | edit source]

Individual, stable differences we have in our activity, emotional arousal, sociable and impulsive.

  • Eysenck's Model of Nervous System Temperament - Interested in nervous system in personality (extroversion vs. introversion). Extroverts have less brain arousal and introverts are the opposite.
  • Gray's Reinforcement Sensitivity Theory - Gray proposed the biological inhibition system (BIS) [avoiding "punishing" scenarios] and biological activation system (BAS) [seeking "rewarding" scenarios]. As an introvert (for ex.), I already have a high level of brain arousal - then the BIS will be more sensitive. Any more arousing situations will feel punishing to me. As an extrovert, I have a lower level of brain arousal - then the BAS will be more impactful.

Sensation seeking[edit | edit source]

  • Neurotransmitters - Play a role in personality. Dopamine is our reward center (looking at an ice cream sundae). People with lower dopamine are prone to more sensation-seeking activities (maybe drug use?). Increased serotonin --> decreased impulsivity.
  • Hemispheric activiy - where in the brain is activity? Right hemisphere = increased reactions to negative stimuli (fear). Just because we see the bio differences, they may [not] be innate. Genes make a contribution to some of the dif. Diff. in our environment also play a role.

Twin Studies[edit | edit source]

Identical vs. Fraternal twins. Identical twins are genetically identical. Fraternal twins are a sperm and egg and a separate sperm and egg that were both genetically separated. Concordance rate for the other identical twin having blue eyes is 100%, but lower for fraternal twins.

Nurture vs nonshared. Twins don't always share the same environment. Not a 100% overlap. Non-shared environments for identical twins: may have same personality and therefore may be treat the same. Non-shared for fraternal twins may be treated differently (sorta like siblings).

Scenario of a nonshared environmental variance:

Jane and Jenny are sisters one year apart in age being raised in the same home by their common biological parents. Jane is very close to their brother Tom, but Jenny does not get along well with Tom. Jane loves their quiet suburban neighborhood, while Jenny finds it boring and would much rather live in a bustling city.

  • Epigenetics - Role of environment on genetic expression. The "activation" or "deactivation" of genes is environmental influences. + stress --> + cortisol through the veins. If a small child is abused, there will be more cortisol running through their system. Their environment turned on a gene to release the cortisol. Factors of the environment can affect the activation of certain genes.

Presence of certain genetic patterns increase the risk of certain psychological disorders (schizo, depression). Highest concordance rate between identical twins than fraternal. The genetics create the risk, then the environment overlaps to determine the actual outcome of any individual (disorders, maladaptive [bad]/adaptive [good] personality traits)

Sexual Identity/Orientation[edit | edit source]

  1. Biological predesposition - There might be some genetic predesposition that contributes to homosexuality. We can see that homosexuality is more common in certain families than others. This isn't a very strong piece of evidence tho because families share environments as well (usually). Hypothalamus regulates sexual activity - there is differences in hypo. activity. Though--simply because we find a brain dif., doesn't mean it is innate. The brain can change based on different experiences that we have.
  2. Biological advantage - Goes back to Darwinism: is there adaptive value in being the gay? Homosexuality has been around for ages... is there a biological advantage to doing this? Does it contribute to the gene pool? Perhaps, it changes something in the social elements that still contributes to the reproductive advantage. Not much evidence for this though, but it is a significant theory.

Mediated Effects of Biology[edit | edit source]

  • Environmental toxins - Something external to the guy is introduced and changes his personality. Mercury poisoning & lead poisoning (see Lead poisoning in toys) is an example.
  • Illnesses - Alzheimers (as it progresses, one loses their personality; can display changing personality traits), strokes, Pick's disease & PTSD.
  • Drugs - drugs that alter neurotransmitters (cocaine), + serotonin (Prozac, used typically for depression); typically long-lasting effects are rare.
  • Tropism - when an organism orients to a particular external stimuli (plant --> light). We orient ourselves to certain environments. In better environments, we grow! What we experience is not random, its our genetics & environment.
  • Reaction from others - People are treated differently because they are physically attractive (same with hostile people). How we are reacted to (expectations) are partially based on genetics (Physical attractiveness stereotype - "Social psychology research has documented that, in general, people expect a physically attractive person to do good and to be good, when compared with someone of average attractiveness").
  • Sociobiology - Studying the evolution of social behaviors. Cinderella effect the idea that bio. children are treated better than stepchildren (similar to kin collection: The idea that even when you don’t have your own biological children, you can increase the extent to which your genes are passed on by helping a family member survive is termed). Have parents evolved to do this? This is in theory. Maybe we want to continue our genes? Men and women have different sexual roles to pass their genes (impregnate women vs. take care of their offspring).
  • Eugenics & genetic engineering - The more we discover genes' role in personality (and modify). Can we get rid of certain maladaptive personality traits?