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Chapter 2

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David Wasserman

Chapter 2 - Zeitgeist: the general intellectual climate of our culture ○ We think about things in ways that have been ingrained in us by our Zeitgeist Thinking about the Biology of Behaviour: from Dichotomies to Interactions - We tend to ignore subtleties and think in mutually exclusive dichotomies - BEHAVIOUR ○ Is it Physiological or Psychological?  ^ question rose to prominence after dark ages (truth was whatever church said)  At ~1400, famines that swept Europe during Dark Ages Subsided □ Interest turned to art, commerce, and scholarship  Renaissance (~1400-1700)  Some Renaissance scholars weren't content to follow dictates of Church, so studied things through direct observation  Much of this scientific knowledge was at odds with the Church  René Descartes (1596-1650) - advocated a philosophy that, in a sense, gave one part of the universe to science and the other to the Church □ Said that universe is composed of 2 elements: a) Physical matter, which behaves according to the laws of nature and is a suitable object for scientific observation b) The human mind (soul, self, or spirit), which lacks physical substance, controls human behaviour, obeys no natural laws, and thus the appropriate purview of the Church  The human body, including the brain, was assumed to be entirely physical, and so were nonhuman animals  Cartesian Dualism - Descartes's philosophy □ Sanctioned by the Roman Church □ Idea that human brain and mind were separate entities became even more widely accepted □ Some people today still believe it ○ Is it Inherited or Learned?  Nature vs. nurture  Most of the early North American experimental psychologists were totally committed to the nurture side  John B. Watson - father of behaviourism □ Give me a dozen healthy infants, well-formed, and my own specified world to bring them up in and I'll guarantee to take any one at random and train him to become any type of specialist I might select - doctor, lawyer, artist, merchant-chief, and, yes even beggar-man and thief  At same time, experimental psychology was taking root in North America, ethology (study of animal behaviour in the wild) was becoming dominant approach to study of behaviour in Europe  European ethology, contrary to North American experimental psychology, focused on study of instinctive behaviours  Instinctive behaviours: behaviours that occur in all like members of a species, even when there seems to have been no opportu nity for them to have been learned □ Assumed entirely inherited  Both the early ethologists and the experimental psychologists were wrong! Problems with Thinking about the Biology of Behaviour in Terms of Traditional Dichotomies - Not long after Descartes's mind-brain duality was officially sanctioned by the church, it came under public attack - 1747 - Julien Offrey de la Mettrie - anonymously published a pamphlet saying thought was produced by the brain ○ Fled to Berlin and was forced to live there in exile the rest of his life - Physiological/psychological thinking: the assumption that some aspects of human psychological functioning are so complex theycan't possible be the product of a physical brain ○ 2 lines of evidence against it:  Even the most complex psychological changes (e.g. changes in self-awareness, memory, or emotion) can be produced by damage to, or stimulation of, parts of the brain Some nonhuman species, particularly primate species, possess abilities once assumed to be purely psychological and thus purel y human  - Asomatognosia: deficiency in the awareness of parts of one's own body ○ Typically involves left side of body ○ Usually results from damage to the right parietal lobe (specifically lesions in the right gyrus supramarginalis and in surrou nding underlying structures) ○ 1985 - Dr. Oliver Sacks's patient - falls out of bed when tries to throw out a human leg he doesn't think belongs to him, doesn't know where his own leg is - G.G. Gallup's research on self-awareness in chimps ○ Chimps have capacity to become object of their own attention when confronted with a mirror  At first reacted like when seeing another chimp  After ~2 days started using mirror to groom and inspect parts of body not seen before ○ When have red spot on brow, start examining it and smelling fingers that touched it Nature-or-Nurture Thinking Runs into Difficulty - Discredited many times only to resurface in a modified form - Factors other than behaviour and learning shown to influence behavioural development: ○ Fetal environment ○ Nutrition ○ Stress ○ Sensory stimulation - Behaviour affected by both nature and nurture ○ New version: "How much of it is genetic and how much of it is experience?"  This version is flawed - it's based on the premise that genetic and environmental factors combine in an additive fashion, rather than through interact ions of the two - Neurons become active long before they are fully developed - The subsequent course of their development (e.g. the number of connections they form and whether or not they survive) depends greatly on their activity, much of which is triggered by external experience - Experience continuously modifies genetic expression Human Evolution - 1859 - On the Origin of Species published ○ Darwin describes single most influential theory in biology ○ He wasn't the first to suggest that species evolve (undergo gradual orderly change) but first to amass huge body of evidence and suggest HOW evolution occurs ○ 3 types of evidence  Documented the evolution of fossil records though progressively more recent geological layers  Described striking structural similarities among living species (e.g. a human hand, a bird's wing, and a cat's paw) which sug gested they had evolved from a common ancestor  Pointed to the major changes that had been brought about in domestic plants and animals through selective breeding ○ Most convincing evidence from evolution in process  Galapagos Islands - 18 month drought - finches with larger beaks to eat larger seeds Evolution and Behaviour - Social Dominance ○ Males try to establish a stable hierarchy of social dominance through combat with other males - either physical or through threats ○ Once a hierarchy is established, hostilities diminish ○ In some species, dominant males copulate more ○ Bull elephant seal  Raise themselves to full height chest to chest  Smaller usually backs down  If not, vicious neck-biting battle ensues  Dominant male - 37% of copulations ○ In some species, dominant females more likely to produce more, and more healthy, offspring - e.g. in chimps  Dominant female chimps more likely to maintain access to productive food foraging areas - Courtship Display ○ Thought to promote evolution of new species ○ A new species begins to branch off from an existing species when some barrier discourages breeding between a subpopulation of the existing species and the rest of the species  Reproductive barrier may be geographical  Reproductive barrier may be behavioural □ E.g. a few members of the species develop a different courtship display ○ Conspecifics - members of the same species Evolution of Vertebrates - Complex multicellular water-dwelling organisms first appeared on Earth ~600 million years ago - ~450 million ears ago, first chordates evolved - Chordates: animals with dorsal nerve cords (large nerves that run along the center of the back, ordorsum ) ○ One of 20 or so large categories, or phyla, into which zoologists group animal species ○ First chordates with spinal bones to protect their dorsal nerve cords evolved ~425 million years ago PSY290 Page 1 ○ First chordates with spinal bones to protect their dorsal nerve cords evolved ~425 million years ago  Spinal bones called vertebrae  Chordates that possess them called vertebrates  First vertebrates were primitive bony fishes  Today there are 7 classes of vertebrates: 3 classes of fishes (Agnatha (jawless fish without scales - lampreys and hagfish), Chondrichthyes (fish with cartilage rather than bone - sharks and rays) and Osteichthyes (bony fish - tuna, bass, salmon, and trout)), amphibians, reptiles, birds, mammals  Recently a 375 million year old fossil discovered with some characteristics of both fish and land animals Evolution of Amphibians - ~450 million years ago, first bony fishes started to venture out of water ○ Fish that could survive on land for short periods of time had 2 advantages:  Could escape stagnant (still) pools to nearby fresh water  Could take advantage of terrestrial food resources ○ The advantages were so great, natural selection transformed the fins and gills of bony fishes to legs and lungs, respectively - so first amphibians evolved ~400 million years ago - Amphibians in their larval state must live in water - only adult amphibians can survive on land Evolution of Reptiles - ~300 million years ago, reptiles evolved from a branch of amphibians - First vertebrates to lay shell-covered eggs and to be covered by dry scales ○ Both reduced reliance of reptiles on watery habitats ○ Reptile doesn't have to spend first stages of life in watery environment  Instead, spends first stage of life in watery environment of a shell-covered egg  Once hatched, a reptile can live far from water because its dry scales greatly reduce water loss though its water -permeable skin Evolution of Mammals - ~180 million years ago, during the height of the age of the dinosaurs, new class of vertebrates evolved from one line of small reptiles ○ Females of this new class fed their young with secretions from special glands called mammary glands ○ Eventually, mammals stopped laying eggs - instead, females nurtured young in watery environment of their bodies ○ Duck-billed platypus is one surviving mammal species that lays eggs - Spending first stage of life in mother - considerable survival value - provided long-term security and environmental stability for complex programs of development to unfold - Today, most classification systems recognize ~20 orders of mammals ○ We belong to the order of primates - ~ a dozen families of primates - apes, old-world monkeys, new-world monkeys, prosimian, hominin, etc. - Several species of Australopithecus thought to have roamed African plains ~5 million years ago before going extinct ~1.5 million years ago ○ Only ~1.3 m tall ○ Small brains but upright posture - discovery of footprints fossilized in volcanic ash ~3.6 million years ago - First Homo species thought to have evolved from one species of Australopithecus ~2 million years ago ○ Distinctive features included large brain cavity (larger than Australopithecus but smaller than modern humans) ○ Used fire and tools ○ Coexisted in Africa with various species of Australopithecus for ~half a million years until the Australopithecus died out - ~200,000 years ago, early Homo species gradually replaced in African fossil record by Homo sapiens - ~50,000 years ago, modern humans began to migrate out of Africa - Big three human attributes: large brain, upright posture, free hands with opposable thumbs (moves in different direction than other digits) ○ Has been evident for hundreds of thousands of years, yet most human accomplishments are of recent origin  Artistic productions (e.g. wall paintings and carvings) didn't appear until ~40,000 years ago  Ranching and farming not established until ~10,000 years ago  Writing not invented until ~3,500 years ago Thinking about Human Evolution - Evolution doesn't proceed in a single line - more like a tree - Evolution doesn't always proceed slowly and gradually ○ Rapid evolutionary changes (i.e. in a few generations) can be triggered by sudden changes in the environment or by adaptive g enetic mutations - About the time hominins evolved, there was a sudden cooling of the earth - decrease in African forests and increase in African grasslands - Fewer than 1% of all known species are still in existence - Evolution doesn't progress to preordained perfection, just better ○ E.g. mammalian sperm couldn't develop effectively at body temperature so scrotal sac evolved - not great design solution - Not all existing behaviours and structures are adaptive ○ Evolution often occurs through changes in developmental programs that lead to several related characteristics, only one of wh ich is adaptive  The incidental non-adaptive evolutionary by-products called spandrels □ e.g. Human belly button - by-product of umbilical cord □ Also, behaviours or structures once adaptive can become nonadaptive or even maladaptive if the environment changes - Exaptations: evolved to perform one function and later co-opted to perform another ○ E.g. bird wings - first evolved for walking - Homologous: structures that are similar because have common evolutionary origin - Analogous: structures that are similar but have different evolutionary origins - Convergent evolution - causes analogous structures (similar selection pressures) Evolution of the Human Brain - Early research into the evolution of the human brain focused on size ○ Assumed size = intelligence → Wrong!!! ○ Whales and elephants have much bigger brains ○ Geniuses didn't have incredibly big brains ○ Larger animals tend to have larger brains - presumably because more brain tissue is need to control and regulate them - Proposal of brain weight to total body weight ○ Humans (2.33%) vs. elephants (0.20%) ○ However problem: shrew (3.33%) - More reasonable approach: compare evolution of different brain regions ○ Study evolution of brain stem separate from evolution of cerebrum  In general, brain stem regulates reflex activities critical for survival (e.g. heart rate, respiration, blood glucose levels) , while cerebrum involved in more complex adaptive processes such as learning, perception, motivation - Over course of evolution human brain has: ○ Increased in size, mostly in the cerebrum ○ Increase in number of convolutions Evolutionary Psychology: Understanding Mate Bonding - Evolutionary psychology: trying to understand human behaviours through a consideration of the pressures that led to their evolution - In most species, mating is totally promiscuous - Promiscuity - mating arrangement in which the members of both sexes indiscriminately copulate with many different partners during each mating period - Mating bonds - enduring mating relationships ○ Most mammals form them ○ Trivers proposed a theory in 1972 - because females give birth to relatively small numbers of helpless, slow-developing
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