Biological Approach Flashcards
Assumptions of the biological approach?
- Everything psychological has a biological basis.
- Our biology is determined by evolution and genetics.
- To investigate the mind, we must investigate the physical brain.
- To understand human thoughts and behaviour we mug investigate biological structures (physiology) and processes (e.g. biochemistry) within the brain and body.
The influence of genes on behaviour: Genotype and Phenotype
Genotype refers to the genes an organism has inherited.
Phenotype refers to traits that are actually expressed.
An organisms genotype which becomes its phenotype can include physical traits such as shyness and temperament.
Whether or not gene is expressed depends on 2 different things: the interaction of the gene with other genes and the continual interaction between the genotype and the environment.
E.g. identical adult twins usually look slightly different because one may exercise more than the other or dyed their hair etc. Despite having the same genotype, the way the identical twin’s phenotype is expressed differently. This illustrates that much of human behaviour depends upon an interaction between inherited factors (Naturs) and the environment (nurture).
Diathesis stress model
Another example comes from studying individuals with depression.
An individual may inherit genes (genotype) which instruct the brain to under-produce serotonin, so the individual is vulnerable and I becoming depressed.
However, symptoms of depression may only be expressed (phenotype) is these genetic factors interact with environmental triggers e.g. stress.
For psychological disorders, role of gene-environment can be explained by refers to the diathesis stress model.
Whether a disorder develops, depends on the combination of the diathesis factors (e.g. genetic predisposition for a disorder) being triggered by stress factors (e.g. Environmental pressures).
1 factor alone may not lead to the disorder; a combination of factors is required.
Method of investigating the influence of genes: Twin studies
Research into genetic basis of behaviour involves twin, adoption and family studies.
Twin studies investigate many pairs of twins and assess how often they share particular characteristics.
The statistic used to measure the chance that 2 individuals share a characteristic is known as a concordance rate - this can be written as a % or decimal. E.g. if 10 pairs of twins are investigated and in 9 pairs, they both have symptoms of schizophrenia, and in 1 of the 10 pairs only 1 of the twins has schizophrenia, the concordance rate would be 90% or 0.9.
What are the 2 types of twins?
Monozygotic (MZ) and Dizygotic twins (DZ)
What are Monozygotic twins (MZ)
Identical twins and share 100% of their genetic material.
0 - sperm
o- egg
O
O O
(shared placentas)
What are Dizygotic twins (DZ)
Non-identical twins and share about 50% similarity of genetic material.
0 - sperm- 0 o - egg - o O O O O (separate placentas)
Concordance rate and MZ and DZ twins
- If characteristic is purely genetic, the concordance rate for MZ twins will be 100% and 50% for DZ twins.
- If concordance rate is significantly higher for MZ twins this suggests a characteristic is mainly genetic.
- If the concordance rate for MZ and DZ is similar this suggests a characteristic is determined by the environment.
Explain the twin study example
Gottesman and Shields 1966 conducted a twin study on individuals suffering with schizophrenia.
This reported an MZ concordance rate of 92% and a DZ concordance rate of 22%. MZ twins are genetically identical and the concordance rate is significantly higher compared to DZ twins - strongly supports the role of genes in schizophrenia.
What is meant by Evolution and Behaviour.
Evolution is the process by which successive generations of organisms change.
The process of natural selection, proposed by Charles Darwin, suggests if an organism is able to adapt to its environment, it will be more able to survive and therefore have a greater chance of reproduce.
This adaptive characteristic may occur due to mutation (random variation) when genes are copied from the parents.
When the offspring reproduces itself, the adaptive characteristic will then be genetically transmitted to its own offspring which will then benefit from the same characteristic.
This continues for each successive generation.
Overtime, an adaptive characteristic will become more common throughout a species. Although this adaptive characteristic is biological, it may underlie a particular way of behaving which helps the organism to survive.
Those without the adaptive characteristic (behaviour) will gradually die out.
E.g. attachment is an adaptive behaviour. Human infants are helpless and require adult assistance for a number of years in order to ensure survival.
Creating an emotional bond to an adult who will subsequently care for it therefore confers a survival advantage.
In addition, food preference is also linked to evolution. Humans have evolved favourable attitudes to particular foods because they aid survival. E.g. high calorie foods. By avoiding certain foods, we are less likely to eat something that will harm us, thus increasing survival chances.
The influence of Biological structures on behaviour: The Brain
The largest part of the brain is the Cerebrum, making up about 85% of the total mass of the brain. The outer surface of the cerebrum is called the cerebral cortex, which is responsible for many of the higher-order functions such as thought and language.
The cerebrum is divided into 2 halves aka hemisphere, with each hemisphere further ./. into 4 different parts known as lobes. Each frontal lobe has different functions relating to behaviour:
1) Frontal Lobe - associated with reasoning, emotions and decision making
2) Pariental Lobe - associated with perception of stimuli and attention.
3) Occipital Lobe - associated with visual processing
4) Temporal Lobe - associated with memory and speech.
The relationships between biological structures and behaviour has been shown in individuals that suffer with OCD. Several areas in the frontal lobes of the brain are though to be abnormal in people with OCD.
The caudate nucleus (located in basal ganglia) normally suppresses signals from the orbital frontal cortex (OFC).
The OFC sends worry signals to the thalamus, i.e. potential germ hazard.
When caudate nucleus is damaged it fails to suppress minor worry signals from the OFC and the thalamus is alerted and confirms the worry to the OFC creating a worry circuit.
Influence of Neurochemistry on behaviour
Neurotransmitters
When nerve impulses reach end of one neuron, neurotransmitters is released. Travels from 1 neuron to next across synapse. There are many different types of neurotransmitters - some trigger receiving neurone to send impulse and stop it from doing so. Excitatory neurotransmitters, are neurotransmitters that trigger nerve impulses in recieving neuron and stimulate brain into action.
Those that inhibit nerve impulses in order to calm the brain and balance mood are called inhibitory neurtransmitters.
Dopamine
excitory neurtransmitter taht is accosiated with our drive or motivation.
Serotonin
inhibition neurotransmitter, to maintain stable mood needs adequate amounts.
E.g. neurotransmitters seen to have role in offending behaviour. Serotonin normally inhibits prefrontal cortex and thought to exert calming inhibitory effect - thought to reduce aggression and offending behaviour.
Low levels of serotonin remove inhibitory effect - leaves individual less able to control their outward expression of anger and aggression and offending behaviour might occur.
Describe the pathway of neurotransmitters
Firstly the chemicals are transported into the axon terminal and neurotransmitters are produced and packaged into vesicles. (Synthesis)
Second step is release: in response to the electrical impulse, neurotransmitters are released into the synaptic gap.
Receptor activation: neurotransmitters cross the synaptic gap and bind to specific receptors.
Inactivation is when the neurotransmitter is re-uptake or broken down in the synaptic gap by enzymes.
