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Chapter 2

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Western University
Psychology 2220A/B
Scott Mac Dougall- Shackleton

Evolution,Genetics,and Experience FIG2.3 January-12-12 12:00PM THINKING ABOUT THE BIOLOGYOFBEHAVIOUR: FROM DICHOTOMIES TO INTERACTIONS - Dichotomies - right-wrong, good-bad, attractive-unattractive ○ Interms of behaviour - is itphysiological or psychological; is itinherited or learned? - ISIT PHYSIOLOGICAL ORPSYCHOLOGICAL? - Rene descartes's philosophy gave one part of the universe to science and the other tothe church (cartesian dualism) ○ Argued that the universe is composed of two elements: 1. Physical matter - behaves with laws of nature (includes human body) 2. Humanmind - soul, self, spirit - obeys no laws of nature ○ The idea that the human brain and the mind are separate became accepted - Soit obv should all be physiological, but many people still cling to the idea that there's a category of human activity that transcends thehuman brain ○ Believed that the pineal gland was the soul something - ISIT INHERITED OR LEARNED? - Nature-nurtureissue- whether humans and other animals inherit their behavioural capacities or acquire them through learning - ManyNA experimental psychologists = nurture - Ethology - the study of animal behaviour in the wild - focused on the study of instinctive behaviour (behaviours that occur in all like members ofa species even when there seems to have been no opp for learning) ○ Emphasized role of nature - Bothwrong - no behaviour isentirely inherited or learned - PROBLEMSWITH THINKING ABOUT THE BIOLOGICAL OFBEHAVIOUR IN TERMS OF TRADITIONAL DICHOTOMIES - Physiological-or-psychological thinking runs into difficulty - Physiological-or-psychologicalthinking -the assumptiontat some aspects of human psychological functioning are so complex that they could not possibly be the product of a physical brain ○ Two lines of evidence against it: 1. Event the most complex psychological changes can be produced by damage/stimulation to parts of the brain 2. Somenonhuman species possess abilities that were once assumes tobe purely psychological and thus purely human - Case 1: Oliver Sacks's account of "the man who fell out of bed" ○ Asomatognosia -a deficiency in the awareness of parts of one's own body  Left side of the body  Resultsfrom damage to the right parietal lobe - Case 2: GG Gallup's research on self-awareness in chimps ○ Even nonhumans, which are assumed to have no mind, are capable of considerable psychological complexity like self-awareness - Nature-or-nurture thinking runs into difficulty - Factorsother than genetics and learning were shown to influence behavioural development ○ Change the nature/nurture dichotomy from "genetic factors or learning" to "genetic factors or experience" - Started asking "how much of it isgenetic, and how much is result of experience?" ○ Thisis flawed b/c it's not additive- they interact - Three general points: 1. Neurons become active long before they are fully developed 2. The subsequent course of their development depends greatly on their activity, much of which is triggered by external experience 3. Experience continuously modifies genetic expression - Amodel of the biology of behaviour - Biopsychologists - single premise that all behaviour is the product of interactions among three factors: 1. The organism's genetic endowment, a product of itsevolution 2. Itsexperience 3. Itsperception of the current situation HUMAN EVOLUTION - Darwin presented three kinds of evidence to support his assertion that species evolve: 1. Hedocumented the evolution of fossil records through progressively more recent geological layers 2. Hedescribed strikingstructural similarities among living species suggesting that they had evolved from common ancestors 3. Hepointed to the major changes that has been brought about in domestic plants and animals byprograms of selective breeding - Naturalselection - the heritable traitsthat are associated with high rates of survivaland reproduction are the mostlikely ones to be passed o n tofuture generations - Fitness - the ability of an organism to survive and contribute its genes to the next generation - Scientifictheory - an explanation that provides the best current account of some phenomenon based on the available evidence - EVOLUTION AND BEHAVIOUR - Two examples of behaviours that play a role in evolution: - Social dominance - Encounters b/w males involve: physical damage, threats until one backs down - this is to establish a hierarchy of social dominance - Social dominance is important in evolution b/c: ○ Insome species dominant males copulate more than nondominant males and thus are more effective in passing on their characteristics tofuture generations ○ Insome species dominant females are more likely to produce more, and more healthy, offspring - Courtship delay - Copulation isunlikely to occur if one of the pair fails to react appropriately to the signals of the other - Anew species begins to branch off from an existing one when some barrier discourages breeding b/w a subpopulation of the exi sting species andthe remainder of the species ○ The reproductive barrier may be geographic or behavioural - COURSEOF HUMAN EVOLUTION - Evolution of vertebrates - Chordates - animals with dorsal nerve cords - evolved 150mya ○ Vertebrates- the chordates that possess spinal bones - Evolution of amphibians - Fishesthat could survive on land for brief periods of time had two great advantages: ○ They could escape from stagnant pools to nearby fresh water ○ They could take advantage of terrestrial food sources - Amphibians - evolved b/c the advantages of life on land were so great that natural selection transformed the fins/gills to legs/lungs - Evolution of reptiles - Reptiles evolved from amphibians - The first vertebrates to lay shell-covered eggs and to be covered by dry scales - Evolution of mammals - We are called mammals after mammary glands - We are in the order: primates - Chimpsare the closest tohumans - Emergence of humankind - Hominins - primates of the family that includes humans - Composed of two genera: ○ Australopithicus ○ Homo (thought to have evolved from australo..)  Composed to two species: □ Homoerectus - extinct □ Homosapiens (humans) - coexisted with australo.. In africa until australo died out - Large brain cavity - Uprightposture - Free hands with an opposable thumb - THINKING ABOUT HUMAN EVOLUTION - Evolutiondoesn't proceed in a single line - We humans have little reason to claim evolutionary supremacy - we are the last surviving species of a family that's existed for a short time - Evolution doesn't always proceed slowly and gradually - rapid changes occur by sudden changes in the environment or by adaptive genetic mutations - Lessthan 1% of all known species are stillin existence - Evolutiondoesn't progress to preordained perfection - Notall existing behaviours or structures are adaptive ○ Spandrels- the incidental non-adaptive evolutionary by-products - eg the human belly button - Notall existing adaptive characteristics evolved toperform their current function ○ Exaptations- characteristics that evolved to perform one function and were later co-adapted to perform another - eg wings (supposed to be legs) - Similaritiesamong species do not necessarily mean that the species have common evolutionary origins ○ Homologous- structures that are similar b/c they have a common evolutionary origin ○ Analogous -structures that are similar but do not have a common evolutionary origin ○ Convergent evolution - the evolution in unrelated species of similar solutions to the same environmental demands - EVOLUTION OF THE HUMAN BRAIN - Early research focused on size b/c of the assumption that brain size and intellectual capacity are closely related - two problems: ○ Itwas shown that modern humans do not have the biggest brains ○ The sizes of the brains of acclaimed intellectuals were found to be unremarkable - False assumption - It'smore reasonable to compare the evolution of different brain regions - Brainstem - regulates reflex activities critical for survival - HR, respiration - Cerebrum - involved in more complex adaptive processes - learning, perception, motivation - Three important points about the evolution of the human brain: ○ It has increased in size during evolution ○ Most of the increase in size has occurred in the cerebrum ○ Anincrease in the number of convulutions(folds on the cerebral surface) has increased the volume of thecerebral cortex (outermost layer of cerebral tissue) - Allbrains are constructed of neurons, and the neural structures in the brains of one species can usually be found in the bra ins of related species - EVOLUTIONARY PSYCHOLOGY: UNDERSTANDING MATE BONDING - Evolutionary psychologiststry to understand human behaviours through a consideration of the pressure that led to their evolu tion - Inmost species, mating is totally promiscuous - Mostmammalstend to form mating bonds though - why? ○ Trivers'theory attributes the evolution of mate bonding in many mammalian species to the fact that female mammals give birthto relatively small numbers of helpless, slow-developing young Thus, it is adaptive for the males of many mammalian species to stay with the females who are carrying their offspring and to  Thus, itis adaptive for the males of many mammalian species to stay with the females who are carrying their offspring and to
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