Chapter 2

• There is a tendency to think in simple dichotomies when explaining behavior
• Descartes argued that the universe consists of two elements

  • Physical matter
  • Human mind (soul, self, or spirit)
• Cartesian dualism


  Views the mind and brain as separate entities
• Brain damage has an impact on psychological functioning

  • Example: Oliver Sacks’s case study of a man with asomatognosia
  • Deficiency in awareness of parts of one’s own body
  • Due to damage to the right parietal lobe
• Chimps show psychological (i.e., “human”) abilities

  • Example: Gallup’s research on chimp self-awareness
  • Chimps spontaneously groom themselves in mirror
  • Chimps examine and touch red mark on their own face seen in mirror
• Many factors have an impact on behavior other than genetics (nature) or learning (nurture)


  • “Nurture” now encompasses learning and environment
  • Behavior is a product of nature and nurture, but genetic and experiential factors do not merely combine in an additive fashion
  • Interactionism
• While Darwin was not the first to propose that species evolve


  • He was the first to compile supporting evidence and suggest how evolution works
  • Darwin presented 3 kinds of evidence
  • Darwin argued that evolution occurs through natural selection
• Just as physical features can contribute to “fitness,” so do behaviors


  • Some are obvious—the ability to find food, avoid predation, etc.
  • Some are less obvious—social dominance and courtship displays
• Evolution of vertebrates


  • Chordates have dorsal nerve cords
  • Vertebrates are chordates with spinal bones
• Evolution of amphibians


  • Bony fishes leave the water briefly
  • Advantages include fresh water and new food sources
• Bony fishes leave the water briefly
• Advantages of leaving the water include fresh water and new food sources
• Lay shell-covered eggs; covered by dry scales
• Reptiles can live far from water
• Develop mammary glands to nurture young
• Humans belong to family hominids, genus Homo
• First homo species emerged from Australopithecus 2 million years ago
• Homo sapiens emerged 200,000 years ago
• Evolution does not proceed in a single line
• Rapid evolutionary changes do occur
• Fewer than 1% of all known species are still in existence
• Evolution does not necessarily result in perfect design
• Not all existing behaviors or structures are adaptive
• Not all existing adaptive characteristics evolved to perform their current function
• Similarities among species do not necessarily mean that the species have common origins
• There is no relationship between brain size and intelligence
• Brain size is generally correlated with body size
• More informative to look at relative size of different brain regions
• The human brain has increased in size during evolution
• Most of the increase in size has occurred in the cerebrum
• Increased convolutions in the cerebrum have served to increase the volume of the cerebral cortex
• Most species mate promiscuously
• Most mammals form polygynous mating bonds
• Humans generally form monogamous bonds
• May be adaptive in allowing more attention to survival of children
• Men tend to value indications of fertility
• Women tend to value power and earning capacity
• Physical attractiveness predicts which women bond with men of high status
• Mate attraction strategies: for women, physical attraction; for men, displaying power and resources
• Men are more likely than women to commit adultery