Nature and Nurture CREATE A CHART NATURE VS

Nature and Nurture CREATE A CHART: NATURE VS. NURTURE The Nature-Nurture Debate

Nature or Nurture? Nature and Nurture? NATURE • The view of the NATIVISTS • “Nature” here refers not simply to abilities present at birth but to any ability determined by genes, genes including those appearing through maturation NURTURE • The view of EMPIRICISTS • Everything is learned through interactions with the environment, environment the physical and social world, more widely referred to as ‘experience’

Example: The Entrepreneur • Discuss - Is the person who starts up a business born with the necessary independent drive, interpersonal skills and creativity etc. “born to run a business”, or are these things mostly learned? • Researchers followed more than 5, 500 students and graduates of five universities: • Initial results indicate that students who take entrepreneurial courses are more likely to launch, run or be employed by a start-up than others • The more insightful finding is that students who took an entrepreneurial course were more innovative than company founders who didn't: • Those students had far more patents or copyrights (75% vs. 19%), new production processes (62% vs. 28%), and new services or products (86% vs. 18%). So much for the "nature" philosophy.

Hypothetical Example: Twins with the MAOA Gene • The MAOA gene comes in multiple variants: – those with the AH variant of the gene are optimistic and resilient to bad treatment – Those with the AL variant react strongly to maltreatment, and often develop antisocial behaviour in response to it • Imagine identical twins, both with the AL variant, are separated at birth: – one was adopted by a loving family – the other was adopted by an abusive family • Discuss: Which child has the greater chance of becoming antisocial? Clearly, the one raised in the abusive family would have a greater chance of becoming antisocial Just because the outcomes are different does not mean that the behaviour isn't 100% genetic. The environmental scenario detection is built into the design of the genes (i. e. the brain circuitry designed by the genes)

How About You? • Can you think of something about you that is clearly the result of what you were born with? with – Please share with the class. . . • Can you think of something about you that is the clear result of how you have been raised, raised or of the experiences you have had? – Please share. . .

History of the Debate NATURE NURTURE • Plato, Plato the Greek philosopher, believed that a child began life with knowledge already present within him • 17 th century, the French philosopher René Descartes argued similarly • English 17 th century empirical philosopher John Locke, Locke said that there were no innate ideas • He believed that the mind at birth is like ‘white paper void of all characters’, a ‘blank slate’

History of the Debate NATURE NURTURE Darwin’s theory suggested • The behavioural that traits were inherited, inherited theories championed by which influenced early Watson(1913) and Watson psychologists Skinner(1938) Skinner explained all behaviour solely in • James(1890) believed James terms of experience that humans beings had innate tendencies which determined natural selection

History of the Debate NATURE • 1950 s - Chomsky challenged the behaviourist account of language acquisition: it happened not just through experience but because human children had an innate language module in the brain • Also in the 1950 s, Burt was promoting the idea that IQ is inherited • The latest move away from ‘blank slatism’ is evolutionary psychology, which explains behaviour in terms of innate factors

Assumptions NATURE NURTURE Evolutionary psychologists assume that behaviour is a product of natural selection Behaviourists assume all behaviour can be explained in terms of experience alone E. g. - Interpersonal attraction can be explained as a consequence of sexual selection – men and women select partners who enhance their reproductive success E. g. Skinner(1957) proposed that a child’s acquisition of language could be explained entirely in terms of rewards and shaping

Re. Perception NATURE NURTURE • Gibson(1979) argued that perception is entirely innate • Gregory(1972) pointed to Gregory the ambiguous and fragmentary nature of most sensory input • The sensory array is sufficiently rich in information for perception to take place without any additional cognitive input • Perception must thus rely on expectations (derived from experience) to complete the perceptual process

GENES! Nature Nurture Nature affects Nurture affects Nature Genes may affect behaviour directly or may exert an indirect effect in a number of ways Experience effects innate systems. The brain has the ability, during development and adulthood, to be changed by experience. E. g. A new study suggests young people are more likely to become addicted to cigarettes if they carry a specific form of a gene that helps clear nicotine out of the liver. E. g. Pascual-Leone et al. (1995) found the region of the brain that controls finger movement increased in size in participants who played a piano finger exercise daily over only 5 days

Arguing the Facts NATURE NURTURE • Twin studies -. 85 correlation in IQ among identical twins vs. . 60 correlation among non identical twins • Flynn Effect - Flynn showed that avge. IQ scores over the world had risen over generations, about 3 points per decade • Authors of The Bell Curve Asian/Asian Americans have a generally higher IQ than white Americans who in turn have a higher IQ than Black Americans • Studies show IQ varies with: • # siblings, malnutrition, • # yrs in school, • social group of the parent home • parent professions & economic status • parent ambitions, • average book reading, • emotional adaptation

Arguing the Facts NATURE NURTURE • Identical twins reared apart show similar IQ scores as those reared together • Schooling and intelligence influence each other A 1997 study showed that delays in schooling cause IQ to drop 5 pts per year and a temporary drop in IQ during school vacations • This indicates that intelligence is mostly genetic • Another study showed a 2. 7 point IQ advantage for each year of schooling

Nature-Nurture: Twin Studies Genetic and environmental contributions to cancers at 28 anatomical sites were studied in a sample of almost 45, 000 pairs of twins from the Swedish, Danish, and Finnish twin registries, some cohorts going back to the 19 th century

Some Results At least one cancer occurred in ~11, 000 persons among 9500 pairs of twins Increased genetic risk was shown for stomach, colorectal, lung, breast, prostate cancers Prostate cancer = 42% of risk explained by heredity Colorectal cancers = 35% due to heredity Breast cancer = 27% due to heredity The implication drawn is that more than half the risk of cancer is due to the environment. Virtually all is due to “unshared” environment rather than common environments (e. g. family diet, in home smoke exposure) For cancer at the common sites in identical twins, the rate of concordance is generally less than 15 percent.

Twin Study: Conclusion • The study has its limitations • But is consistent with other results • These results indicate a major environmental role in carcinogenesis • It’s not just the genes

Nature and Nurture: Last Word It is said that a journalist once asked psychologist Donald Hebb which contributes more to personality, nature or nurture? In response, Hebb asked, “Which contributes more to the area of a rectangle, its length or its width?