Perspectives in Psychology


Sex and gender

Sex is biological aspects
   - Chromosomes
   - Genitalia
   - Sexual identity

Gender is social aspects
   - Identity
   - Gender role

There are strong opinions on the differences between males and females, people can get fired from jobs, canceled for saying there's a difference

David/Brenda Reimer
  Born male, genitalia replaced at 2 months, raised as a girl, told of incident and reassumed male identity 

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Development differences


  • More time spent working (diligent)
  • Better verbal abilities
  • More time grooming
  • More infant contact and play
  • Greater attention to faces


  • More time spent playing
  • Better spatial abilities
  • Better arithmetic reasoning
  • Greater physical aggression
  • Greater attention to mechanical movements
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Bateman's principle
   - Male reproductive success depends on the number of mates

Men report more sexual partners and hold more sexually permissive attitudes
   More likely to have sex in a shorter period of time
   More likely to agree to casual sex

r=0.66 for men           r=0.26 for women
   looking at physiological cues of arousal snd reported arousal correlation
      Females may have automatic genital response - lubrication could be a defense mechanism

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Other sex differences

Men prefer youth and health in partners
Women prefer resources and social status in partners

Men are more likely to commit violent crimes
   Tempers may flare when there's competition

Men more likely to engage in risky behaviour
   Risk can sometimes reap rewards

Men and women have different personalities
   16 personality factors showed effect size of 2.7 (Very large)

Men have a higher concentration of testosterone
   - makes them more sexually motivated, energetic, aggressive

Difference in toys chosen (humans and monkeys

Men more likely to do STEM in some countries

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Gender similarity hypothesis

Has since been disproven


There are differences but also similarities between genders
  e.g, overlap in height differences  

Hyde argues that 77% of psychological sex differences are only very slight

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Testosterone changes development in foetus

Congenital adrenal hyperplasia - overexposed to testosterone
   - more male behavior
   - more likely to be attracted to females
   - less preference in sex of friends
   - slower language development
   - less eye contact

Thoughts that testosterone could be linked to autism

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Bateman's principle

Darwin suggested that males were eager as the costs of transporting sperm was lower than the costs of transporting eggs for females

Bateman found that in a specific species of fruit fly, the number of offspring increased with the number of mates for males
He predicted that this was because single eggs are more costly to produce than single sperm, so the number of offspring was limited by the ability to produce eggs

Trivers drew attention to  postzygotic parental investment - feeding young, defending against predators
Predicted that the limiting factor would be the sex with the largest parental investment

  • Males showed greater variance in number of offspring
  • Males showed greater variance in number of sexual partners
  • There was a stronger relationship between reproductive success and mating success in males

Sexual selection will only take place if the likelihood of success is dependent on possession of a particular trait

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Bateman's principle continued

Bateman's gradient = regression line between reproductive success and mating success
Sex with steepest gradient faces strongest selection pressures on traits that better mating success

Relationships between reproductive success and mating success
single-mate saturation
diminishing returns
intermediate optimum

Females can benefit from multiple matings
   - reduced infanticide risk, assurance of fertilisation, material gains, genetic benefits

Males can be more prudent due to energetic costs of sperm production, courtship, copulation

Intense competition in one sex doesn't necessarily lead to choosiness in the other
Females choosy when male heavy, little paternal investment, considerable variation in quality
Males choosy when female heavy, a lot of paternal investment, considerable variation in quality
Both sexes choosy when encounter rates are high
Neither sex is choosy when low encounter rates

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Humans with regards to Bateman's principle

Males exhibit higher mean variation in reproductive success

Large inter-population variation in ratio of male and female variance in reproductive success

Serial monogamous  societies have similar ratios to polygynous
Ratio of variance in male and female success is greatest when male mating success varies more

Western societies, men more likely to remarry than women
   - longer reproductive lifespan

Polygynous societies more common, though rare for males to actually take on more than 1 wife

If parental investment high, polygyny is costly and increases in reproductive sucess are not linear
Mate saturation/diminishing returns

Strong positive correlation found between wealth and reproductive succes in modern and traditional societies

Strong female cpmetition occurs when high variation in male quality

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