Brain and behaviour

• The brain is the control centre of our body, controlling all bodily functions.
• the brain is an organ, physical object, living tissue, consisting of nervous tissue
• nerve cells are neurons and glial cells and are cells within the nervous tissue
• behaviour is any form of observable action/ reaction or a person or animal in response to external or internal stimuli; examples are: movement, speech, attitude, blushing, thinking
• most behaviors consist of a mix of inherited and learned actions, Examples: Sucking reflex in newborns = inherited; Eating later in life = strongly influenced by learning and culture
• This mixture varies considerably from species to species: Smaller, simpler nervous system --> narrower range of behaviors that depend mainly on heredity; Larger, more complex nervous systems --> more complex behavioral patterns that depend on learning
• the mind-body problem: Dualistic versus monistic philosophical views & Spiritualistic versus materialistic views
• behavior is action, not physical but observable
• men and chimpanzees share a common Hominin ancestor BUT we do not descend from chimpanzees
• Hominins = 1. common ancestor originated ~ 5 million years ago 2. primates who walked upright 3. all hominins evolved from this ancestor 4. humans only surviving hominin species
• Australopithecus = “southern ape”
• Homo habilis = “handy man”
• Homo erectus = “upright man”
• Homo sapiens “knowing man”
• Encephalization quotient (EQ) = actual brain size/ expected brain size (relative to body weight) (e.g. cat = average domestic animal --> EQ 1; Australopithecus --> EQ 2.5; Homo sapiens --> EQ 7.0, so: our brain weight ~tripled in 4mio years)
• What is so special about the human brain?

  Modern humans have the largest brain size relative to body weight
• How did our brain get so big?

  • lifestyle adjustment (social group size, hunter-gatherer, eating fruit, use of fire (cooking) --> more time for social interaction
  • Efficient brain cooling: circulating blood functions as a radiator (like in a car engine), enabled homo sapiens to maintain high metabolism (= more horsepower) --> 2% weight, 25% oxygen, 70% glucose
  • Neoteny: retention of juvenile features in the adult animal; adult humans closely resemble the infants of gorillas and chimpanzees (e.g. large head relative to body size)
• Is a larger brain also a better brain (within species)?

  Answer: no

  e.g. Einstein's brain weighted only 1.2kg, which is less than the average adult male brain (~1.4kg)
• Most behaviour is not innate but acquired during life & culturally determined