Evolutionary/Biological Models of Personality

Evolutionary Psychology

• We tend to have personality characteristics that, phylogenetically, helped our ancestors reproduce

• If our ancestors were more successful at reproducing, then they were more successful in spreading their traits via genetic information

• This led to . . . US!

How do we select mates?

• “Inclusive fitness”

• We look for mates who will increase our chances for survival and the survival of relatives

  • Good parenting skills

  • Altruistic behavior (huh?)

Kin Altruism

• We are attracted to people who favor relatives —> promotes successful passing of genes

Reciprocal Altruism

• Unrelated people help eachother, which is good too! The risk of helping another is less than the benefit of being helped by the social network formed.

  • Again, promotes successful passing of genes

Who do we scorn?

• Cheaters! Freeloaders!

  • People who will not help as much as they are helped

The value of family

• The classic framing effect is found in humans

• You live in a family of 600 people infected by disease; Choose

  • Guaranteed 200 live

  • 1/3 chance that all live; 2/3 chance that all die

• People select guarantee

• You live in a family of 600 people infected by disease; Choose

  • Guaranteed 400 die

  • 1/3 chance that all live; 2/3 chance that all die

• People select risky option

• Now you live in a family of 60 people infected by disease (more realistic)

• It doesn’t matter how the question is asked

• People select risky option because, phylogenetically, a clan of reduced numbers has decreased probability of surviving and passing along DNA

Unfortunately…

• Because environments/societies have changed, some of our current traits have little value (and, at times, can be problematic):

• Food selection

  • Sweets and high caloric foods (take advantage of food while possible)

• Personality

  • Aggression

  • Extreme jealousy

But many are… functional

• Negative affect; fear of:

  • snakes

  • strangers

  • heights

• Positive affect

  • Helps lead us to goals (hope; reward)

  • Laughing indicates safety; enhances bonds with group

Emotions

• Accurately perceiving and expressing emotions are critical to social bonding, and to reproduction

• Emotional abilities allow us to adjust our behavior to solidify social ties:

  • See needs of others, allowing us to share our goods and strengths with them

  • Cooperate to protect against threat

  • Social support even improves immune function

    • Giving and receiving!

Evolved Psychological Mechanisms

• Processes which evolved to solve particular problems associated with survival/reproduction

  • Sexual jealousy

  • Sexual attraction based on appearance

  • Sexual attraction based on male’s ability to provide

  • Sexual attraction based on youth

  • Imitation

Sexual Jealousy

• Greater in males than females

• At least historically, it was uncertain whether children biologically resulted from the “father”

  • Thus, men tend to pay closer attention to their partner’s sexual fidelity

Sexual Attraction Based on Man’s Ability to Provide

• Given that women have a fairly limited opportunity to reproduce (relative to men), they want to ensure that offspring are cared for

  • Historically, children with fathers present were more likely to survive

  • Affluence, to a degree, also predicts survival rates

Jealousy Again

• Men tend to be more jealous of sexual infidelity

• Women tend to be more jealous of emotional bonding between partner with other women

  • Want to make sure that father continues to support the family

Sexual Attraction Based on Physical Appearance

• Good looks are a signal of health

• Men and women prefer bodies, faces that are symmetrical

  • suggestive of “good” DNA and proper neural development

• Men prefer a low waist:hip ratio (~.7)

  • Optimal for reproduction

• Women prefer strong chin and cheekbone structure

  • Indicative of high testosterone levels

Physical Attraction Based on Youth

• Men generally prefer younger women

  • Greater number of reproductive days lay ahead!

Imitation

• Children, as part of play, imitate adults

  • Essentially, they “practice” and “learn” adult behavior

  • This helps enable them to utilize behavioral tendencies that have been successful from one generation to the next

    • Why do we know these behaviors are successful, you ask?

Cultural Transmission (very Jungian)

• Cultural “laws” are passed down from generation to generation

  • Not all biological

• Culture is passed down via:

  • Stories

  • Religion

  • Tools

  • Technologies

  • Social organizations

Biological Predisposition for Personality

• Temperament: Twin studies show this to be highly heritable, and highly consistent across the life span

  • Emotionality

  • Activity

  • Sociability

  • Self-regulation

Babies (Thomas and Chess)

• Babies given new objects with which to play

• 40% easy – happy and interactive

• 15% slow to warm up – withdrew and seemed mildly distressed

• 10% difficult – withdrew, were irritable —> high risk for psychiatric symptoms in childhood

• Rest are variable

Jerome Kagan’s Model

• 21-month-old children with their mothers

  • Younger/Older male/female experimenters come into room to offer new toy and play

  • Fairly reliably, children would either play or cling to mothers

    • Inhibited type

    • Uninhibited type