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Intro to Psychology Notes
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Class notes from VU Amsterdam course on Intro to Psychology and its Methods
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Psychology Lecture 1 NotesBy Somansh – former Prince of Nigeria
Overview
Ø Genetic basis of life
Ø Evolution by natural selection
Ø Genes and behaviour linkage
Genetic Basis of life
• Does violent person have violent genes
o Varied in past
o 70s and 80s belief – Behaviour (incluiding violence) was influenced by
environment. Because ideology influenced their scientific thinking. As if they
wanted to believe that capitalism and strict parents created violent kids.
§ Dutch dude/prof called Bowhouser wanted to find biological basis of
crime, like – does testosterone increase criminal behaviour. Fellow
scholars and media trolled him and he quit science.
o In 90s, the heritability studies became common. Studies found that genes
were the basis of violence and other behaviour. Thus, refuted that
environment was main cause of violence and other behaviour. Scholars like
Rich, Udit ? wrote a book on it.
o Today we know that both genes and environment affect behaviour.
• Genes and biology
o Human cells have 23 pairs of chromosomes (46 in total). Chromosomes are
mostly a coil of DNA strings/threads/wires.
o DNA is a large string of alphabets [ built of bases A,T,G, and C ]. Combo of
alphabets is called genes (words). Genes are read by a little chemical dudes
(tRNA ,mRNA) in the cell and they tell ribosomes (located just outside
nucleus of cell) to make proteins based on these words. These proteins help
in making and working of muscles, eyes, skin, immune cells, neurones,
blood, brain etc. Basically DNA builds and runs the body.
o ‘A’ always pairs with ‘T’. G always pairs with C. These base pairs are held by
Phosphate and sugar chemical structure.
o Not all parts of DNA leads to creating proteins (non-coding DNA). We still
don’t know what it does, completely.
o Basically, genes give the blueprint of every part of our body, and how they
will behave, mostly. But food, exercise, social life, random events also affect
our body and behaviour.
o This is where heritability comes in.
§ It answers the question: how much do genes affect a trait (violence,
eye colour, height, depression, IQ ), and how much does
environment affect a trait.
o Gene expression - not all genes are expressed at all times. Every cell in body
has same genes but the genes that are ON in a cell determine it’s function.
, Neural cells, liver cells, skin cells have same genes but very different due to
their gene expression.
§ Methylation – Methyl molecules come from
environment/behaviour/random events. These Methyl molecules are
attached to a gene, and turn it off. Thus restricting its expression. It
stops whatever gene it touches.
§ Thus, cells are affected by environment. Thus, environment affects
genes, genetic expression and consequently affects behaviour.
§ Spielman ? 1967 study showed that cells from embryo become
teeth, when planted on mouth area, and become skin when planted
outside the embryo. Cleary, the location (environment) of genes
affect their expression.
o So, not every protein encoded in the genes is created all the time. Hence, a
person with genes for good muscles may not have a fit body coz she didn’t
exercise. In other words, the genes for good muscles were not expressed.
• Genotype – Set of genes of a specific organism
o Phenotype – features/traits/behaviour of a specific organism. It is an
outcome of genes and environment’s interaction.
o Monozygotic twins (2 persons born out of one sperm fusing with one egg)
have 100% genes in common. But they differ in many features – behaviour,
hobbies, skin health, fitness etc. Clearly, environment, not genes, led to
these differences.
o Alleles - Each baby gets 23 chromosomes from mother and 23 chromosomes
from father. Except sex chromosomes X and Y, the genes on every
chromosome from mother’s side is similar to genes on chromosome from
father’s side. For example, mother and father’s chromosome number 11 will
have similar pair of genes at same position. These similar genes are called
alleles. Think of alleles as genes that are located at the same position in
chromosome, and do similar task. But vary slightly.
§ Note: NOT EXACTLY SURE ABOUT THIS ONE. VERIFY LATER. There
may be multiple alleles of a gene in a population, such as alleles of
eye colour genes: blue, green, black, brown. But a person gets only
two genes out of the total genes available. One from mother and
another from father.
§ If the two genes (alleles) at same position are identical, the person is
homozygous for that gene pair. If they’re somewhat different, the
person is called heterozygous for that gene pair.
o In the alleles (genes), one gene may be dominant and other may be
recessive. In that case, dominant gene will express, and recessive won’t. To
illustrate, assume a gene ‘B’ leads to blue eyes (when expressed), and gene
‘G’ leads to grey eyes when expressed. If G is dominant and B is recessive ,
the person will have grey eyes. Recessive genes are expressed when both
alleles are recessive.
§ Sometimes both genes are recessive or dominant. Then, a weird
mixed expression of genes happens.
o Not every gene leads to one trait. Many genes may influence one trait
(height/Schizophrenia) – called Polygenic inheritance.
, o Or one gene may influence multiple traits.
• How does an organism end up with a genome ?
o Due to natural selection – explained by Darwin.
o Genes that are expressed and lead to advantageous traits (good hunting
skills, sense of smell, vision) allowed an individual to survive long enough
and reproduce. Thus passing the genes. With time, genes that help in life
survive and thrive. Though, some not so useful genes also slip through, which
may turn out to be useful after many generations, or turn out to be lethal.
o 3 conditions for natural selection
§ The population of organisms must have variation in genes.
§ Individuals with genes suited for the environment survive and
reproduce more than others.
§ Traits are thus passed from parents to offspring.
o Example – a moth of brown colour used to blend with the tree colour, so
birds couldn’t eat it. But in cities, the brown colour didn’t blend well with
dark polluted walls. So, moths of darker shades survived more in polluted
cities. After pollution restrictions, brown moth was back.
o Evidences of evolution
§ Fossil evidence – dinosaur, bird, human, fish fossils over millions of
years.
§ Similar genomes of various organisms.
• Chromosome 2 of humans is a fusion of two chromosomes of
anthropoid apes that existed thousands of years ago.
§ Pseudogenes – inactive genes in DNA. Maybe functioned in the past
but now just sits there. Humans have 2000 such genes. We carry
genes required to make Vitamin C from glucose. But one part is
inactivated. Eating Vitamin C rich foods must’ve inactivated the gene.
So, another proof of evolution.
§ Distribution of species across Continents.
• Japan – Earlier connected to a continent. Diverse species.
• Hawaii – Oceanic island, never connected to a Continent. Lacks
diverse animals like freshwater fish, reptiles. Only long
distance travelling species could colonise the island – like
birds.
• But how does it explain evolution ?
o Evolution doesn’t improve the species, nor does it create the best genome. It
only creates species adapted to the environment. A fish has genes suited to
water life but on land they are useless.
§ Evolution doesn’t create rigid behaviour patterns. It may change
when needed.
• Nature nurture debate
o Scholars used to argue if nature(natural build/biology/genes) or
nurture(environment, outside events, parenting, random events) shaped
the organism
o Today we know it is both, so the debate is irrelevant now. Nature and
nurture interact and shape the organism
, • Who we are and how we behave is determined by – how our genes behave in a
certain environment.
• MAO study
o Persons with low MAO activity combined with parental mistreatment were
more like to commit crime and show aggressive behaviour.
o Low MAO didn’t automatically lead to higher aggression. Mistreatment alone
did increase aggression, but when combined with low MAO activity,
aggression shot up. Thus confirming: nature and nurture influence
behaviour.
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