Question Where did your personality come from? Random Environment Genetics

“Twin Study” Dizygotic (DZ) “Fraternal” No more genetically related than siblings Monozygotic (MZ) “identical” Genetically identical

“Twin Study” Example Give 100 MZ pairs a measure of Extraversion Calculate a correlation r =.50 Give 100 DZ pairs a measure of Extraversion Calculate a correlation r =.30

Twin Study Why is MZ > DZ? Heritability Coefficient –The proportion of behavioral variance that can be explained by genetic variance (MZr – DZr) x 2 ( ) x 2 =.40 Heritability of Extraversion = 40%

Behavior Genetics Note: Doesn’t really study behavior or genetics directly Typical Heritability of personality traits is around 40%

Behavior Genetics Genes matter! Heritability are almost always greater than zero Not all of personality is determined by the environment or random chance

Genes and Environment Environment can affect heritability Example: –Height and food intake

Genes and Environment Genes work though the environment to affect behavior

Genes and Environment Genes gave him bad eyesight

Genes and Environment Wearing glasses caused him to be teased and rejected by the opposite sex

Genes and Environment Due to these interaction he becomes introverted Note: Introversion due in part to genes, but only came about through environment

Genes and Environment Diathesis-Stress Model A genetic predisposition can cause a person to develop maladaptive behaviors in stressful situations

Diathesis-Stress

Behavior Genetics Limitations All humans are highly similar to each other –Share 90% of genes BG is only looking at differences in the remaining 10%

Behavior Genetics Limitations Saying “A father shares 50% of his genes with his daughter” really means “A father shares 50% of the genetic material that varies across individuals with his daughter” Heritability Coefficient –The proportion of behavioral variance that can be explained by genetic variance

Behavior Genetics Why do you have two feet? –Environment? –Genes? Heritability of arms would be zero!

Behavior Genetics Thus, if there is no variation due to genetic influences heritability will be zero

Why would some elements of our personality and body not vary across people? Important for survival!

Evolution Applied to human behavior: Behaviors are present because in the evolutionary history of human species, these behaviors were helpful or necessary for survival. –Survive –Reproduce

Evolution Examines the shared 90% of genes Asks: How a behavior pattern could have been adaptive during the development of the human species

Evolution Not forward thinking –e.g., giraffes neck Don’t want to consciously do this (we are wired) –Its not about what you consciously want, its about what you ultimately try to do!

But I don’t want to have kids! You would not be here if SOMEONE didn’t have children. What caused them to reproduce? Sexual urges (do you think you would be here otherwise?) Your sexual urges are based on an inherited instinct Even if you don’t WANT to reproduce, your sexual urges make it more likely that you WILL have children Other examples: pornography, etc.

Evolution Morality and evolution Naturalistic Fallacy If it is natural it is good e.g., you and kids Political objections are irrelevant from a scientific standpoint

Evolution Works at the level of the GENE, not the individual “You” really are not even important (or any animal) in an evolutionary framework it is all about the GENES! –“The Selfish Gene”

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“The Blind Watch Maker” Someone finds a watch on the ground (highly complex) Someone must have made it How can complex life result from random chance (mutation) and simple selection rules?

“The Blind Watch Maker” Group Activity –Need: Blank paper Pen or pencil Straight edge

(1, 2) (3, 4) (5, 6)

How to play 1) Mark a small dot anywhere on the paper 2)Roll the die 3) Mark a second dot on the paper exactly half way between your last dot and the vertex indicated by the rolled dice (do not connect the dots) 4) Repeat steps 2 and 3

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“The Blind Watch Maker” Product appears to be complex and planned Only created with: –1) Random chance (die) –2) Simple rules (move halfway)

Evolutionary Psychology Relatively new field Identify a common behavior pattern Ask how it could have been adaptive Note: Examining “human nature” Research has tended to focus on –Sex (mate selection and strategies) –Aggression

Evolutionary Theory Please think of a serious committed romantic relationship that you have had in the past, that you currently have, or that you would like to have. Imagine that you discover that the person with whom you’ve been seriously involved became interested in someone else. What would distress or upset you the more (only select one)

A) Imagining your partner forming a deep emotional attachment to that person B) Imagining you partner enjoying passionate sexual intercourse with that person

A) Imagining your partner trying different sexual positions with that person B) Imagining your partner falling in love with that person

Reporting more distress about sexual infidelity

Physiological Responses Sexual Image....Imagine your partner is having sexual intercourse with this other person Emotional Image....Imagine that your partner is falling in lave and forming an emotional attachment to that person

Physiological Responses Measured Electordermal activity –Electrodes on hand (nervous) Pulse rate Electromyographic activity –Brow (nervous)

Sexual Image Emotional Image

Results Males tend to get more upset (physically and self-report) with sexual infidelity Females tend to get more upset (physically and self-report) with emotional infidelity Why?

Evolutionary Psychology Reproductive success Note don’t make the errors of: “that’s not what I want” “that’s not moral so it must be incorrect”

Evolutionary Psychology Facts: 1) Females always know that their child is their own 2) Males never completely sure of this 3) It takes more resources for a female to produce a child than a male

Evolutionary Psychology Males most reproductively successful if they have multiple mates –It is “cheap” to reproduce –Less cost associated with each offspring It is a waste of time to stay with one woman and one set of children –If he leaves they will probably survive –If he leaves he can reproduce with another person

Evolutionary Psychology Females most reproductively successful if they have one mate who helps provide –More “costly” to reproduce –More cost associated with each offspring If male stays –Increases likelihood children will survive –If children survive will reproduce in the future

Evolutionary Psychology Women more sensitive to “emotional infidelity” more likely to keep mate around (and therefore more reproductively successful) Men more sensitive to “sexual infidelity” more likely to avoid caring for offspring not his own (and wasting resources)

Personal Ads I am very energetic, have a great sense of humor, honest, thoughtful, romantic and love to cook. I am looking for someone who is romantic, outgoing, has a great sense of humor and of course likes kids and animals. If you are out there maybe we can get together and talk.

Personal Ads I'm a very honest and true person who is down to earth. I'm sensitive with a big heart yet strong minded with lots of ambition. I have a lot of love inside to give to the right person.I'm a one man women who is very faithful and committed.

Personal Ads Because I am a professional individual, I don`t believe in dating at the office to avoid "politics and rumors." Just got back into the dating loop, (just broke- up) But, Just got a new convertible! Want2go4 a ride?

Personal Ads.. I enjoy dining out occasionally, "in" is where I prefer, hands down. When you have a pool table, air hockey, swimming pool, jacuzzi, and a karaoke "system" (not machine) at your disposal, you tend to be content staying home for the most part. I work hard for what I have....

Results Top 3 qualities men and women look for Intelligence Kindness Love

Results Women tend to seek: (Provider characteristics) Tall and strong –80% say they want a male over 6 feet Good earning potential Older males

Results Men tend to seek (Child bearing characteristics): Younger women Attractive –Full lips, clear and smooth skin, clear eyes, lustrous hair, and good muscle tone

Why? Men and women seeking the same thing –Greatest possible likelihood for successful reproduction Women bear children –Youth related to success (reproductive peak) –Attractiveness related to successful reproduction e.g., lips, complexion, etc. Men's contribution is support –Most men produce healthy sperm (regardless of age)

But...

Evolutionary Theory Why are some women attracted to highly unstable but extremely attractive men? “Sexy Son Hypothesis” Different reproductive strategy –Hope offspring will also be “sexy son” Mate with more women in the future