Lecture 2 - The Nature-Nurture Debate

What mechanisms makes evolution work?

• natural selection

• sexual selection

What are the steps of natural selection?

• Step 1: individuals differ → variation

• Step 2: more individuals than resources → struggle

• Step 3: offspring resembles parents → heritability

• Step 4: individuals have features that help with survival and reproduction → adaptations

• Step 5: some individuals are better adapted to their environment, and offspring inherit these adapted features → natural selection

What does natural selection result in?

• differential reproductive success

What is sexual selection?

• some features are selected because these are attractive to sexual partners

nucleus

• each cell contains one

• contains two complete sets of human genome (one of father, one of mother)

• contains 46 chromosomes → 23 from each father/mother

chromosomes

• made of proteins called deoxyribonucleic acid (DNA)

• contain genes

gene

• discrete unit with hereditary information

alleles

• variant of sequence of nucleotides at a particular location → matching genes; one from our biological mother, one from our biological father

• are dominant (A) or recessive (a)

Homozygous

• AA and aa → if both alleles are dominant or recessive

Heterozygous

• Aa and aA → if alleles differ in dominance/recessiveness

What kind of influences do genes have? (3)

• passive → parents offer environment that child passively have to accept, but that will be relatively consistent with your genes, because you share their genes

• evocative → based on the genes you have, you show certain temperament, which evoke certain reactions in environment

• active → based on your genes you’re looking around for certain environments

differential susceptibility

• some individuals remain stable, under whatever circumstances (”dandelions”)

• other individuals vulnerable under negative conditions, but can excel under positive conditions (”orchids”)

How can epigenetics occur?

• through DNA methylation

• through histone modification

DNA methylation

• methyl marks added to certain DNA bases repress gene activity

Histone modification

• combination of different molecules can attach to “tails” of proteins called histones

• these alter activity of DNA wrapped around them

altricial species

• in which the young are incapable of moving around on their own and are dependent on their parent(s) for food and safety for some period of time after hatching/birth.

precocial species

• in which the young are physically mobile and able from the moment of birth or hatching.

nativism

• the view that many skills or abilities are ‘native’ or hard wired into the brain at birth, the result of genetic inheritance.

empiricism

• the view that humans are not born with built-in ‘core knowledge’ or mental content and that all knowledge results from learning and experience.

cognition

• mental activity, such as attention, memory, problem-solving, thinking, intelligence.

mental age

• concept introduced by Binet

• individual’s level of mental ability relative to others

chronological age (CA)

• a person’s actual age, as opposed to their mental age.

intelligence quotient (IQ)

• a measure of a person’s level of intelligence compared to a population of individuals of approximately the same age

• IQ = (MA/CA) x 100 → old formula

• IQ = 100 indicates average intelligence

• IQ >/< 100 indicate, respectively, above and below average intelligence

standardised test

• a test of a psychological characteristic, such as personality, aptitude, or intelligence, that has been standardised on a representative sample of the population.

g

• the term used to denote general intelligence → always written as g and never G

heritability

• a statistical measure that describes how much of the variation of a trait in a population is due to genetic differences (rather than environmental differences) in that population

• dramatic increase in heritability of cognitive development from early to middle childhood

→ 1 = perfect correlation, 0 = no correlation

What should you watch out for when interpreting heritability?

• heritability = measure of variance, not biological mechanism → if there’s little variance, heritability is higher

• changing over populations and time

• measure at population level, not individual level

genetic determinism

• the hypothesis that people become who they are as a consequence of their genetic inheritance.

environmentalism

• the hypothesis that people become who they are as a consequence of the learning and experiences they have had throughout life.

familial resemblance

• the resemblance between relatives whose genetic relationship to each other is known.

monozygotic (identical) twins

• genetically identical twins, developed from one ovum and one sperm which divides into two shortly after conception. Such twins have the same genetic make-up.

dizygotic (fraternal) twins

• individuals who are conceived at the same time but result from two eggs being fertilised by different sperm. Thus, they are like regular siblings and share half of their genes.

missing heritability (problem)

• the failure to find any of the genes associated with cognitive abilities.

Genotype

• an individual’s inherited genetic makeup → genome whole genetic makeup

Gene x environment interaction (GxE)

• when different genotypes respond to similar environmental factors in different ways to create individual’s phenotype: genotype and environment interactions (GxE) → phenotype (P)

Phenotype

• the interaction of genetic and environmental influences to create an individual’s physical appearance and behaviour

Phenylketonuria

• a rare genetic mutation which, if left untreated, results in severe mental retardation and learning difficulties.

Chronic obstructive pulmonary disease (COPD)

• a collection of lung disorders such as emphysema and bronchitis and airflow obstruction. People with COPD have difficulty breathing.

Fatty acids

• building blocks of fat in our bodies and in food we eat

• have many important functions in body, including energy storage

environmental drift

• changes in developmental functions that result from, and are in the direction of changing environments.

Flynn effect

• an increase in the average intelligence quotient (IQ) test scores over generations.

Raven’s Progressive Matrices (RPM)

• a culture-free non-verbal intelligence test with items arranged in order of difficulty.

malnutrition

• a serious condition that occurs when a person’s diet does not contain the right amount of nutrients

• malnutrition means ‘poor nutrition’, caused by lack of food and/or inadequate diet

poverty

• minimum level of income deemed adequate in a particular country

• in practice, this level is significantly higher in developed countries than in developing countries

absolute poverty

• in poor/developing countries: limited access to food and/or clean water

relative poverty

• in developed countries: households which earn 60% or less than median income

compensatory education

• offers supplementary programmes/services designed to help children at risk of cognitive impairment and low educational achievement succeed